I have no idea on this one?

Well what's the feeding schedule look like and are this autos are photoperiod

In my limited experience I'd say you added stuff and didn't mind water content in the root zone. Stick to a nutrient recipe and runoff means balance in the rootzone.

From look root issue. That wavy wrinkles idicates roots ir cold temp and roots. Intake fan next too or overwater and root bound started. That plant has to drink sliw even if top soil looks dry while lifting pot it will be heavy, watering like rest will only increase problem. From picture my guess. Peroxide waterining to revive with oxygen roots and good watering regime if i am right.

All of them are getting the same amount of light? I thought about lack of N. Bright leaves might signals that. Anyway, its hard to say if used nutri's arent known..