Most likely a virus take the curled part of and trash it don't clone a diseased plant because all the clones will have it and it's spread by insects or a pair of scissors. what soil are they growing in? If it were me I would trash the whole set up and start fresh soil and plants fighting that shit is almost futile.
well none of the plants have had anything like this affect them and i do handle them alot now that they're in flowering(ill go in and rough em up a bit) and it dousnt seem to be spreading. plus i already cloned it haha. but with it falling behind in resin production it'll prolly get trashed anyway. i did have one of the slower growing plants have curled leaves but that was due to a ph problem and she went back to normal once it was fixed.
i started them in half n' half of miracle grow and back yard soil. after dealing with them getting burned alll the time i switch to pure back yard dirt and compensated with extra nutes. it dries out fast but thats good for me as i tend to over water.