Your plate coral does NOT look to be receding back from its skeleton from what I see in the pictures. That would be a cause for worry if it starts receding.
The plate corals that I had were short tentacle ones and they changed looks like that during the different light cycles in my tank.
They also inflated and moved around some on my sandbed. All of which, I think is normal for them. I only fed mine about once a week & they did good.
They are an easy to care for coral so I think as long as your tank parameters are good, it will be OK. If you are trying to feed it daily, cut back on that.
I traded both of my plates in on my 2nd Scolymia. Wish I would've kept one but I needed more room on my sand bed for my scolys.
Good luck with yours