When to use fertilizers when watering

I would not feed every other day at full dosage, seems very excessive!
If you wanna cut your dosage in half, that might be fine, tho.
You gotta see what works for you.
I'm a bit more worried that you're blasting your plants too hard with too many lights, and it looks awfully close from that perspective.

If you're in coco or any other soilless medium; you'll need to feed every time. If you're in soil, I believe the rules of thumb is water, water, feed.

that plant in the back row has some issues going on. what medium? what nutes?