A pic of the whole plant would help.
Maybe too much ferts or what I'm seeing from your leaves are they got wet when the lights are on or they lay together and transpire and the big light burns them. make sure the leaves do not get wet during light hours. It's OK during dark.
Maybe a hot spot from your light.

What is your runnoff PH ? that's more important. If your container is 3 gallons then you should water with 3 gallons. Yes 3 gallon. Pour it through slow. This makes sure it is watered to the bone and then it needs to dry out good and repeat. Watering too often and with too little is a common problem. The soil just doesn't get wet to the bone. Small amounts don't flush bad things out and build up fert salts