Is the leaf color because of some nutrient need or...

Hi mate, it really looks like light burn. And be careful with the dosage of nutrients, maybe you should low them a little bit.

You have a few issues here , all pointed out by previous comments , also watering , you need to water to runoff , every two - three days depending on weight , for your next grow water less , and with less nutrients 👍 To runoff

It looks like you had spider mites at a point in time. But now it seems that your light maybe to close to the plant try pulling the light away to about 18 inches if possible.

i went back a few weeks and it looks like you've got a few issues. you seem to have spider mites you can see tiny spots on top of the leaves just below the buds and some nute burn (looks like nitrogen burn) and yes i agree i also see some light burn. so i would say to get a magnifying glass or a loupe and look at the underside of the leaves (they are very small) if you have mites i would advise game over for this plant if not ( though i doubt it) flush and only use plain water for atleast a week. lastly you would need to raise the light i always err on the side of cation with leds and would say more like 50 cm or 20 inches away

It is heat stress, the tops are too close to the lights, 15 cm (6 inches) is too close for that kind of wattage; try 25 to 30 cm (10 to 12 inches). Literally you lights are burning the top part of your plants