The size of the pots is ok, when they grow in the ground as in nature, they have acres of room for root growth.
The lighting at 18/6 is perfect.
Lights at 30 inches maybe a tad too far away, about 24 inches is better.
No fan is no good, they need air movement to be able to transpire properly.
All your pictures look like a much too wet substrate, water only once the top 2-3 cm have dried out completely.
The damaged leaves will not recover, but your new growth should be fine.
Add a fan, reduce the watering, decrease the light height and start feeding more regularly, with half strength and things should pick up.
A dose or three with some seaweed tonic/extract would also help them recover.
Remember too, you are on a new adventure with growing and to get familiar with what it takes, takes time.
Hope this helps, Organoman.