That yellowing plant,
How old is it? and have you feed it yet? Like 1/2 strength nutrient mix?
also I noticed that purple in the center of your new growth on the one seedling...I've seen that happen to a few of mine in the past. I never really linked it to one thing, like under/over feeding or say environmental issues, ex: temps and humidity...but I do know that its a sign of something wrong. As every plant that shown that in my grow, had stunted growth and took time to recover.
So maybe someone can elaborate for me and you , and can identify what that is..
When it happened to me I thought it was from things being too cold. I was in hydro and My rez temp wa falling below 50 degrees also my ambient air was cold too. Also seen it before with clones and seedlings but never figured out why....I doubt its genetics....