Some of the leaves are having some yellow dots on ...

With no EC/PPM information it's hard to give an accurate diagnosis. That the pictures are under purple light does not help. Anyway I think it's calcium deficiency, due to either soft water (if your water PPM is lower than 200, there's a high chance this is the cause); or it could be due lockout caused by nutrient excess, those burnt tips support this theory.

The yellow tips indicate nutrient burn. The yellow spots could be a calcium or phosphorus deficiency, but could also be a sign of spider mites. Good luck!