Great pics Phil, tanks looking good.
The pit on the Clowns heat looks a lot like what is generically referred to Hole in the head disease. Don't panic though, it technically is not a disease, it's more a symptom or indicator of one (or more) of numerous problems. This fish may have been in a system with some problems prior to you getting it and developed the "pitting". Sometimes the pitting is bad enough that it wont go away, much like a scare, once it's there it's perminet. If it has not gotten any worse since you have owned it, I would not be to concerned about it. This is also just a guess, I really couldn't say for sure what it is but if it has remained the same for an extended period of time it most likely is nothing to worry about.
I can't tell in the pics what your talking about in the Purple tangs eyes. I see the white or haze but it's tough to say. In person does it look like cataracts? There is a fluke (trematode) that causes that appearance but members of the zebrasoma genus are not notorious for carrying it (but they can). Do you have a grounding probe in the aquarium water? If you don't, you should consider it. If you have a multi meter, put it on DC, ground it and put the positive end in the water, see if there is a bunch of electricity in the water. Excessive electricity can cause some of the concerns your describing.