Kinda lost here. (pics inside)

Hey guys,
Been having some plant trouble for quite some time and I don't really know what's wrong.
Plant has been in flowering for 5-6 weeks and growth is stunted. Leaves are yellowing and some were even rotting but it seem to have stopped now .

Watering them every 4-5 days with a liter of water. I'm also using some bio bloom very sparingly ( I think I gave them fert 3 times since they started flowering). I think I got the ph too low for the past few weeks and it might be the reason why they are having trouble.
Been having a lot of Fungus gnats problems so that's why I removed the first few centimeters of soil to replace it with sand so the bugs would have a harder time and it seems to contain the problem a bit. I also use a pyrethrum based insecticide that I spray on the surface of the soil to kill the pests.

So many things could go wrong. is it the insecticide that is running through the soil damaging the plant ? is it the ph inbalance, is it a lack of nutrients or an overfert of some kind ? :s

These are White widow feminized seeds.
4 plants growing indoors under a 400 W light.


Help would be greatly appreciated!

Hard to tell in the tent. Take them out and get better pics if you can. It almost looks like heat problems. Also how big are your pots? 1L every 4-5 days seems like they are not feeding. In 3 gallon pots during flower I usually give about 1.25 gallons of water every 4 days to get just a little runoff.

Another thing it could be is root rot. Fungus gnats mess up your root system. Can you see any roots through the holes in the bottom of your pot? If so are they white and healthy or brownish or tan and smelly? Another thing is the sand you used, was it prewashed? Before I use any play sand I rinse it really good. Play sand is prewashed but not rinsed very well so flush it good before adding it to your topsoil.

And the last but not least suggestion that you may want to check first is pH.

But if you get better pics up under regular light we may be able to help you better. Good luck.

Hey thanks for the quick reply man.
Pots are 8-10 liters, I'm not really sure anymore, they are 30 centimeters wide at the top that's all I can tell you for certain.

The sand wasn't washed before I used it but it was only put in place like a week ago. I had these problems long before, I think if the sand is going to harm my plants, it's not showing yet :s.

As you can see from the shot under the pot, roots look pretty healthy :3 gotta love clay pots.

The roots may be growing out the bottom in search of food and water. Do you water til you have 20% runoff? 1L at a time sounds to me like you are not wetting all the soil and you may have dry spots in your mix. Next time you feed/water use a whole gallon or 4L and feed em pretty well. That stage in flowering they should be getting fed at least once a week at almost a full dose of a well rounded nute solution. But if you never fed them a full dose work your way up to full and if you see the tips start to burn then back off. Good luck.

They look hungry for N and P.

If they are 8-10 liter pots and your only giving them 1 liter of water a piece. That's not enough man. I'm in week 4 of bloom and i give each baby a little over a 1/2 gal of water each, or until there is about a 1/2 inch of runoff in my bottom tray.
Looks like some N is lacking too, use some CalMag + or like Vitaboost pro or something like that.
I also wouldn't leave sand packed on the tops of the plants for long as it seems like that would help cut off the circulation of air through your soil properly.
All i did to get rid of my gnat problem is hang like 10 fly strips, put a 1/2 cup of apple cider vinegar between every plant. And let my soil dry out for 1 extra day, but in ur case i wouldn't let it dry out very much. Cuz i think ur underwatering.
Yes, the roots look healthy, but because ur roots are popping out (assuming because they are looking for water) those roots out the bottom are going to prolly die, because they are exposed to light and air.

I just watered them with 2 liters for each plant and have a good runoff already. Some of the saucers (not sure it's the correct term) are full of water already so I'm not gonna add 2 more liters or I'll soak the floor. Gave them a good dose of feed to go with.
The water where I live has a natural 7.0 PH and I think they have received 5.0 or 5.5 ph water for the past 8 weeks so I didn't use any ph down this time. I'll see if it helps the soil balance its ph and help the plants back to life !
Thanks for the help guys.

@MrGreen 187
I used some yellow fly strips too to get rid of the gnats, but to no avail, in 10 days the strips turned from yellow to black from the overwhelming number of gnats that got stuck on them, and I still had some flying around and running on the soil.

I'm thinking I will remove the sand soon, get some new one and rinse it properly this time.
Do you think I should worry that much about air circulation in the soil ? I mean I'm using clay pots and they let a little air and water pass through so it shouldn't be as bad as If I was using plastic pots.

dude u need to get some crashed glass and put that in the top part of ur soil that should cut them up as they walk over it put mesh over ur vents to stop them coming in the fresh air ducking hover 2 times a day and keep ur room clean.keep pets away as they carry shit that u dont want water 2 times a week and feed once then if the plant can take more food then give but less is more when growing weed. u need lots of c02 so put straws in the sand to the soil this will help

Dude, don't put crushed glass in ur soil!!! That has bad idea all over it.

So ur tap water is a 7.0, but ur bringing the PH down to 5.0 - 5.5 before each water?? Pot plants perfect PH level of water they like is 6.5.
Oh, and get rid of those ceramic water catcher saucers. Get some bigger deeper plastic ones. The ceramic ones are too snug around the base and barley hold any water.
Water each plant just a bit til you see a bit of water running out the bottom of the plant, then move to the next, then when ur done go back to the first one cuz by then the plants will have sucked back up the water in the tray and hit em with a bit more water.
I like to let just a tiny bit of standing water (very little), the plant will stop drinking when its full. But because of ur gnat problem, i would not let any standing water sit there.
The gnats love standing water.
The nice thing about plastic pots are they are lighter, they have more drain holes which allow the water to spread and drain out more holes allowing the water to reach the bottom edges of ur plants and bucket.
You only have 1 drain hole which may also cause ur plant to suffocate, you plants need air flow like us, but that 1 drain hole in the middle when pressed down on the bottom ceramic saucer is kinda sealing it and not allowing air to flow though the soil, that along with the sand on top of the soil is causing ur plant to suffocate. The roots need to be spread out but that 1 holes is forcing them to go straight downward and not outward like they should, that why they are hanging out of the bottom like that.

The saucers are actually not ceramic but plastic. They are just the same color as the clay pots but they're made of plastic trust me

Regarding my ph problem: I used a liquid ph tester (the ones where you get 5ml of water and get a few drop of chemical and check the color) To get a good ph. Then I tried to remember how much ph down I put in my water and put the same quantity everytime.
Been doing it for the past couple grows, but it seems I have slowly increased the quantity of ph down without noticing. last week I checked the ph with the last few drops of the product I have and it gave me a 5 / 5.5 indication.

That's why I'm not entirely sure of the ph they have received. I will go back to putting some ph down in lower quantities to get closer to the 6.5 mark but I'm out of ph tester, and since it's gonna be my last grow I don't really want to spend any more money.

Ceramic or plastic, the ones that come with the ceramic pots are to small. You only have one drain hole so the moment you put it down on that saucer it seals the hole up and doesn't allow very much air uptake through your soil. which ur roots need to survive.
Get rid of that tester, it's only good if you own a swimming pool.
Just buy a digital PH pen, i got mine at a local shop for $30. And it's a life saver. PH 6.5!! Every time!!
The issue i see with the way your doing it, is that your PH level, may stay the same if it's plain water, but the moment you do a nute watering your PH won't even be close to what it was with the plain water.
A proper PH pen is one of the most important tools in your arsenal of pot growing utensils..........a must!! Your plant could already be in a lockout situation. If it were a low PH it can be locking out Cal, Mag, and Phos