If a fish is scratching, that means that there is an external irritant of some sort. That can effectively mean many things, but the most common reason is external parasites. Water parameters in the main display (as well as its size) would be a good starting point for troubleshooting the problem. Unless there is a unifying reason I can gather from your water parameters, it is hard to pin down.
For one thing, neither fish is what is considered "easy." Even worse, the parrotfish should not be kept in home aquaria at all. Most refuse to eat as you have witnessed and slowly starved. Even then, they have a very specialized, high-algal diet, also including coral, live rock, and other associated benthic organisms. That is a tough diet to continue giving in the aquarium. Beyond that, they get unreasonably large.
Any extra info would help out tremendously, in any case.