So one of my seedlings is starting to yellow. The one next to it is doing fine. Same strain and everything. I have watered at the same times and with basically equal amounts. Don't have any Idea why this is happening but here are my specs 320 Watts Cfl 24/7 Started in rockwool cubes and moved into dirt. (Which I truly believe to be nute free) Temps around 75 Humidity about 40% ( I know its low its the season) Water with ph of about 6.5 I water every third day but moderately.
What kind of nutes are you using? Try to lower the ph a little bit, to around 6.0...maybe even 5.8... Water a little more often, maybe once per day.
Ok, then yeah, i would water more frequently, and adjust the Ph of the water a little bit. Lower it to about 6.0.