That is what I was worried about, and that is why that white spot was a concern.
The tank is too young, too small and the specific gravity is off, IMO. That is acclimation shock, the "melting" aspect. It may, but is very unlikely to survive. It may be dead already. Hard to tell from the pic, but I strongly discourage trying another or ANY reef safe star (please do not try the much smaller red Fromia, or "bali star" which will have the same fate).