If none of the hatchets seem to be showing any problems like open wounds, ulcers or bruising (other than the one that was injured) then I wouldn't worry about a few scales. A fish will lose scales once in a while just like a bird loses a feather or you and I lose a hair here and there, even without a specific injury or cause. It's natural and the scales will regrow. Don't get me wrong, fish do not shed their scales like a dog or cat sheds its fur or like an invert sheds its skin as it grows, but they do lose scales on occasion. As someone whose kept a large variety of aggressive cichlids, I generally see scales fairly often if I look for them.
The first source may be the hatchet that was injured. Since it suffered a bit off trauma some scales may have fallen off. The other source may be from multiple fish as a matter of course. It may very well be a bit of both (my guess). Regardless, fish skin and scales heal and grow much, much faster than mammalian skin and hair.
As fish keepers we normally don't notice this as the scales are small and blend into the substrate and get vacuumed from the substrate. They may end up in the filter. If you look for them, I would be surprised if you can't find the occasional scale in the future.
Yup, or just a natural occurrence.
As for treating the ich with meds or not, there isn't a wrong or right answer. Like I said, I've never had luck with the high heat method and use meds immediately. Others have used the high heat method with great success. An on-going disease or parasite infection can be stressful to fish, but so can medications. You've kind of come to a crossroads where you'll have to decide which way to go is best and do what is best for your fish based on your observations.
WYite