[Reef Junkie]

Not that it's the problem, but a little coralline can help insulate the heater and trick it into thinking it's warmer then it is.

Thermometers are good, but your tanks temperature gets it's coldest in the middle of the night when you aren't watching it.

I'd just do a little maint on all of your equipment.

It's hard to say if it is in fact the pox, it does show some signs of being the pox. Double check for predators or irritants. ie. Nudi's, snails, worms, Hydroids, aiptasia...

Also try doing some water changes, that has shown to help. Just get the temp right before adding the new water.