Yep. That tiny bit of reflective tissue is enough. I have vermetids that kill mine occasionally and even a corallite seemingly free of tissue can still have just a tiny bit in the center. Slow, but that's all it takes. You should be cup feeding those to drive growth. I buy distressed stn frags all the time from lfs, dip them in nothing, blast feed, and regenerate fast.
You could go as far as feeding it in a separate dish in the mornings which people have done or if that's a hassle, place clear cup over it during the mornings and inject coral specific food onto the frag and let it directly eat before lifting cup
