Well, it stared getting kinda cold here. Max temperature morning is 25°C and night min 20°C inside tent. I'm sure it's not from heat stress, maaaaaybe from light, but really not pushing it too much.
but toxicity isnt what youre dealing with nor are the symptoms normal to what toxicity is. nitrogen toxicity is leafs curling in on its self and super dark green. what youre experienceing what i can see is he lack of nitrogen.
Too little light total. I’ll believe 400 under his 2 little bulbs when a PAR meter shows it. Even if 400 it’s too little light for flower. Low temperatures don’t help with LED.