Definitely looks like a bleached mag, and it is bleached, not white. The long tentacles could be a sign of it being a healthy specimen as far as infection goes, but obviously watching it closely for deflation is the only way to know for sure. IME, aside from the short stubby tentacle variety, the longer tentacles can be a sign of decent health because even a sick mag that's inflated usually has shorter tentacles than it would in a stable environment with good health. Bringing one that bleached back will be a tough battle, but possible in the right hands/tank.