I agree, at only 20 days old, I wouldn't think it was a nute problem...
I was looking at my soil and one of the 2 that I mixed with(Farfard, black earth something) was .2-0-.1, so perhaps I'm seeing a phosphorous deficiency? Other soil I mixed with was a Promix, can't remember the exact one, but it was one of their organic ones.
It was 2:1 (Farfard: Promix), and then I added 20-30% vermiculite.
I'm fairly certain the PH is correct. I've been watering with PH ~6.5 and the one time I watered till run off, I tested the run off PH and it was 6.8.
So if the PH is correct, meaning no lockout is going on, next would be nutes no? And since I haven't given anything, and the numbers on my soil seem moderate/low... I would think adding nutes would be the next logical step.
I could be completely wrong though
and if so, tell me.
I've noticed that today, they are standing quite erect... reaching for that light. I would assume that's a good sign.