doesn't look like overwatering, as the top of substrate looks dry.
So, if doing a regular wet-dry cycle for your substrate, lowering lights can definitely make a plant floppy... it could also adjust to it... if you see any leaves paling or it never perks up, it's not adjusting, it is merely being abused :) trial and error is all you can do for each new seed you grow, not being a dick about it.
if recent behaviour rules out watering and other issues, then i'd chalk it up to lowering lights and switching to bloom schedule. Hold the status quo for a bit and then react if it takes a nosedive. it'll bounce back in a week if not related to watering or other issues. if you have been feedign FF from beginning according to their directions, you'll be safe to ease off for a while i almost can guarantee that.
in the end there are a ton of factors to consider. check pH, check tds etc.. rule out things that are don't involve screwing with the plant or it's soil. if any recent behaviour rules out the things i suggest, ignore my suggestions.
The curl is definitely nutes related... again, be conservative. Irrigate water-only unless you see an issue to help rule out that possiblitity. You are in flower, so i'd be very careful about how long you do this.