I’ve had that same wrasse and he refused sand. He preferred to hide in the rock and make the slime cocoon like some wrasses do.
After qt I placed him in the dt after lights out. I saw him in the corner bent in half Like he was crippled. Fearing the worst I put him back in the qt where he stayed in that condition for a couple days. Then one day he was swimming normally. No idea why it was like that for a few days.
My guess at the time was maybe the salinity was a bit off and he was shocked somehow.