Do you have good ventilation? Also is that aluminum foil? Aluminum foil can creat hot spots. It really is hard to say. I would guess it has something to do with the soil. If it has time released fertilizer then I would say that is the problem. I have some outdoor herbs that have not grown one bit in 3 months in some miracle grow extended release fertilizer! It’s crazy.
Post some more pics without the blurple light, which also could be an issue since plants need more then red and blue light.
Ps who knows, maybe you also got bad genetics. It happens.
Hopefully by herbs you mean Parsley... Cilantro..
Oh yeah, i would never put cannabis in cheap soil. My brother in law, who is a little slow, and dont listian bought bags of chicken manure admentment for his soil. Even filled up 2 15 gallon pots. I went and saw his garden, every single plant was in lock out. And even till this day he says because they are cheap, 7$ a bag when fox farm is only 11$, lol