looks like a mg deficiency - but I germinated and have 1 foot plants growing in ocean forest under 400watt hortilux blue (18/6) and have not even thought about adding mg or other nutes nor have I had nute problems at all except for maybe some limited purple in the seedling stems which is gone now. So at the same time I can't imagine you have a soil problem.... plus you cut it down with perlite supposedly
For what its worth I germinated in MG organic soil under cfls (24/0) last time, and my seedlings ended up with the same spots and the same yellowing on lower nodes - I threw those away and started over in ocean forest with a 100-watt flourex flood light from home depot - those are the one footers that are under mh now - their whole life (planted july 20th) they have been lush green and are very far along, considering they only had 100 + 4*27w for their first 15 days.
just a thought, what is your relative humidity? - for what its worth when my seedlings ended up like this, they were in the same room with a window ac, keeping the air around 80f/25hum (lights on) - I am not sure if the very dry air had anything to do with it. The other difference between that attempt and my current success was 18/6 vs 24/0 last time.... read the do roots grow in the dark faq for more info
For what its worth I germinated in MG organic soil under cfls (24/0) last time, and my seedlings ended up with the same spots and the same yellowing on lower nodes - I threw those away and started over in ocean forest with a 100-watt flourex flood light from home depot - those are the one footers that are under mh now - their whole life (planted july 20th) they have been lush green and are very far along, considering they only had 100 + 4*27w for their first 15 days.
just a thought, what is your relative humidity? - for what its worth when my seedlings ended up like this, they were in the same room with a window ac, keeping the air around 80f/25hum (lights on) - I am not sure if the very dry air had anything to do with it. The other difference between that attempt and my current success was 18/6 vs 24/0 last time.... read the do roots grow in the dark faq for more info