Shriveled Seedlings

Hello!

New medical card-holding grower here. I've been pretty good at growing veggies in soil from seed, but now that I'm trying to grow in hydro I can't even get the seedlings to last more than a week without them shriveling up to nothing! It makes me sad because I see these beautiful looking babies get about an inch and a half tall and then bam! overnight they shrivel up to nothing.

You can see daily photos of the grow here:
http://www.growkeeper.net/growurls/caligabe/

I had high hopes for plant #11, but last night it just took a turn for the worst and I don't think it's reversible. There's nothing green left to grow.

So, I'm growing Northern Lights in rockwool. Seeds were purchased through Attitude and Nirvana. The rockwool was soaked in water with ph down until about 5.3. They were germinated on a heat mat under a plastic dome and then moved out of the dome under CFL's once they sprouted above the RW.

The light is a T5 with 4 6400K tubes, rated up to 6800 lumens. The light is on 24/0.

I'm not using any nutes at this point. Since I can't get them to last more than a week or so, I've never had the opportunity to start them on any nutes. I've done this three times so far and each time the same thing happens. About a week after they sprout, they shrivel up and die.

I'm concerned maybe I'm using too much light for the babies? Even though the light doesn't put off that much heat, it definitely gets warm in the nursery so maybe they get cooked?

I keep the T5 about 10 inches away from the babies to prevent this from happening. The first time time it happened, the light was only a few inches from them so I keep backing it away hoping it will help.

My water is also a concern. I use filtered water through a small boy filter. It comes out about PH 8 and 300 PPM. I use PH Down to get it back down to about PH 5.8-6.0 and use that to water them. I have a bucket of water and I carefully "dip" the bottom of each rockwool cube in the bucket twice a day to keep it moist. I also spritz them with this water a 3-4 times a day. I give the bucket of water a good stirring before watering to aerate it.

I don't have a temperature / RH gauge in the nursery yet, but I can tell it's getting somewhat warm in there - but the lights are not uncomfortably warm for me to touch at all. I'm going to move my temperature gauge from my main tent (that I've never got a chance to use) to my nursery so I can get some readings on RH and temperature shortly.

I appreciate any thoughts or tips anyone may have!

Thanks,

Caligabe

The temperature is at about 79 degrees in the nursery and the RH is 53 - this is with the poly open during the day. I close up the nursery at night using poly velcro'ed to the CFL support frame to keep most of the light in so I'm sure the temperature gets higher. I'll seal up the poly now and see how far the temp rises.

Yep, when I seal up the nursery, the temps go sky high - 87 degrees and RH goes down to 39%. Probably not ideal for seedlings. So, I probably either need to leave the nursery open at night or figure out a way to ventilate better.

Crap. All these little seedlings wasted because I didn't have a temperature gauge where I needed it.

The rw is too wet, prob from the start. Have the cubes 50% wet max at all times and dont mist, there is plenty of water in the rw. Too do this weigh a cube saturated and another dry and split it down the middle, before long you will know the weight by feel.

Thanks for the reply, BUDS! The rockwool cubes feel almost completely dry each time I water them - so dry that it almost makes me think the seedlings are dying due to lack of water. The couple times I watered once per day before I switched to 2x/day, the cubes were most definitely 99% dry - very, very light. Now, even twice a day I feel like they're not holding enough water between waterings - they might be 50% - 25% saturated, but I wouldn't know without weighing them. Is it better to let them dry out completely? They're shriveling up, almost like the leaves are slowly burning, turning brown and curling upwards and inwards until there's no green left.

I'm starting to think it may have been a heat issue - even with the poly open so the nursery gets fresh air, the temp is 76-80 degrees. With it closed it was getting close to 90. Maybe the heat is drying out the cubes faster than usual? I don't understand how the humidity is so low in there. The RH in the room outside the nursery is close to 50%, but when I close the poly the RH inside the nursery falls below 40%.

I'll try weighing the RW to see what the saturation is before each watering - thanks for the tip!