some yellowing on the upper leaves

[op1]

hello ron, hope all is good with you. have 11 tomato plants in the garden, been there for about a week. im noticing some yellowing on the upper leaves, and was wondering if this could be due to a lack of nutrient. the solution i prepared is about 1/4 strength (for seedlings). when should i graduate to stronger solution? can i jump into full strength- or should this be done gradually? seedlings are about 6" tall and~ 24" from the 400wt hps. as always, much thanks for your help. op

[Ron]

Something's not right. Could be low nutrients. I am having the same problem. Let you know when I figure it out.