First time grower with yellowing leaves etc. Please please help me :(

I am a very keen to learn noob 4 weeks into my first grow. I decided to go with barneys vanilla kush seeds and use a 600w light in my 1x1 tent plant setup. They started off perfectly and I was really proud of them but over the last couple of weeks 2 out of my 4 plants have gone from perfect green...to light green....to slightly yellow.. And now yellow fan leaves with brown spots appearing. I use canna coco and have purchased many nutrients... For veg stage i have canna coco A&B, but have recently purchased canna rhizotonic as I was told it might help them a bit?? The new growth is coming through but although it starts green it turns yellow after a couple of days and as a first time grower this is literally like watching a young child screaming out for help but not being able to know what it needs. I have tried flushing... Under feeding, Adjusting the light height and creating more air flow but no luck I'm getting that comforting green look back into my kush plants please someone help me? I will be more than happy to upload pics if someone is patient enough to kindly guide me through this website. p.s I was considering including some bat guano in my next feed as it could be a nitrogen deficiency that is being stubborn? But to be honest I have been reading soo much information on the Internet that I literally don't even know where to start. It could be nitrogen, it could even be magnesium due to slight brown spots appearing? Anyone that is kind enough to help me will be great fully appreciated.I would love to upload pics but as I only have access to an iPad at the moment it's not possible so I'm sorry and I know it will be harder to diagnose but any advice will really help me. Thanks you guys! Joe

Please provide some details such as; Air quality temp, ph and nutrient composition and purity - all of these can contribute to yellowing. Plants are normally affected within 72 hours and this has already been going on for a few weeks you say; provide some more information about your plants and your routine. Also, do you have quality equipment that can check the essentials such as water, nutrients, ph, etc.?

Hello auto thanks for trying to help I have in and extractor fans and a 6inch rotating fan..the ph I am getting used to and on my reader it comes in at 6.0 to 6.2 at all times after adding the a and b ... My only substance I use is canna coco.

I don't have a full on routine I tend to drizzle feed them once or twice a day which seemed to be doing ok I literally just have the four pots at the bottom of the tent and give them their 18hours light.... But it's all done by hand. As a noob I can't know for sure but I would say that the feeds that I give to them aren't too little or too many. I really wish I could upload some pics as I am sitting with them now feeling that i should pray for them or something... I'm really upset that this is happening. Is that info good enough of are there any other particulars that will help? Thanks again for your help

Check your PH for nute lock. Also you posted this in the wrong section. I'll report it for a mod to move it.

Ya, you locked out nutes, homie. I would flush with a very low mix of cal/mag, veg nutrient, and VITAMINO if you can get it. I had a buddy call me up and have me race over to his house. I foliar fed with Vitamino and flushed that mix, and turned a 2 week long problem around in 2 days. You have to flush! Make sure your water is between 5.8 and 6.0.

Flush and use some cal/mag..helped me with the same thing