Possibly too much soil in the pot. If the pot is too full, most likely there is no moisture (and by extention...nutes and additives when old enough to need them) getting to the lower root zone(s).
Is that a terra cotta pot? The clay inherently allows moisture to escape, compounding the problem. Also, roots stick to the terra cotta, making transplant sometimes tricky. (won't easily 'slide-out' of the pot)

If in a humid region, or if growroom is consistently humid, and you are using Panda film...be careful of trapping the moist air between the wall and the film. (mold) Using fluorescent-tube lighting, the reflective film is unnecessary. By the time the flouro light travels to the film, and gets reflected back twords the plant...most lumens have scattered. The film does protect walls from overspray, tho.

Keeping plants close (2-4 inches max) to the fluoro tubes is best. Don't forget to keep the air circulating around them, too.
Rusty Trichome Reviewed by Rusty Trichome on . 10 Days old, Northern Lights (Sensi), FFOFS, Poss PH? My friend is a med patient and let me take a pic of her plants because she is worried. I told her I think it's PH but who knows. The first pic had 4 leaves when it came from the seed and has new growth coming from below the first set of leaves and above. Pretty strange. But it appears to be in the worst shape out of them all. Only a few are having this problem. She sprayed them with Safe-Soap. The first week the seedlings grew around 58ºF-65ºF. Now they are steady between 72ºF and 82ºF Rating: 5