I must admit he had no noticeable white spot to me, but that is nowhere near as important as his skinniness.
PBT are scaleless fish, so whitespot is normal in a captive environment. The whitespot grab on to scaless fish easily.
If a PBT stops feeding properly, its all over.
As long as he eats WELL while you there Fay, it should be fine.
The PBT will be sweet with everything else in tank also Fay.
Tangs are awesome...you'll get hooked!