Feed confusion

They are heavily overfed, would not feed anything , till you transplant them and gave time for setting up.

looks like u overdid with N and now u get PK lockout

Yes, what the colleague says can also be the case.

Also someone said lack of oxygen. I only recently learned u should aerate ur water with a fish tank bubbler for 20-30 min b4 watering ur plants it does help especially after the seedling stage

That's what the lower leaves show, but based on the upper ones I would say that it could soon be overdoing it with n, which is why this seems like a lack of oxygen to me...mainly when the plant has nowhere else to take nutrients, it pulls them from the leaves and starts from below, but it would also show up on the edges of the fan leaves, while that's not the case here.

Looks like they’ve got to be transplanted but I’m personally not an expert at identifying issues. However I do autos in peat pots too. If I don’t transplant them Within 2 weeks they also get yellow leaves. Prob bc it needs more nutrients than seed starter soil in a 3 inch peat pot and adding nutrients in a small pot “probably” burns it too but again not an expert at the identification stuff just possibi

This looks like a lack of nitrogen, but I would say that these plants lack oxygen. Wait for someone who grows inside to give you an answer.