Yellowing leaves on Petunia Seedlings
I have started quite a few petunias from seed this year, and some of them are beginning to turn yellow-ish.
My first thought was a need for fertilizer, but the ones that are turning yellow are not the largest/oldest seedlings (I began several different types at different times as the seeds arrived). They are still quite small, between 4-6 tiny leaves. It seems to me that if the older larger seedlings are not showing signs of fertilizer lack, then the others shouldn't either.
I dont fertilize at all until they are developing at least the second set of leaves, and then use a very diluted fert, every time I water.
The older seedlings are Waves, the yellowing ones are not - could they have different needs? I cant think of anything else that is different, though I may have them in a different starting mix.