Welcome to AA!
Hmm, interesting. Your temperature is a little low IMO
, and Ive seen my softies close up when it gets too high, but never messed with it at the lower range. Perhaps something to consider is to bump the temp up a few degrees and see.
How much flow is in the tank? And are the corals in question in a high flow or low flow area?
What type of water do you use for water changes, and how often and how large do you do them?
These answers might help us figure out what's going on.