Hi,
In my opinion 9 out 10 problems that arise with our fish are bacterial, very often these conditions go unnoticed until it's to late and a secondary infection ie.. fungus, fin rot a condition that we notice sets in.
I think your fish could have the early stages of HITH but it doesn't seem too bad, it's debatable whether it can ever be cleared completely or just put into a dormant state. If you can stabilize the HITH the fish could go on for years, without problems but beware if the fish gets stressed or sick this will cause the HITH to erupt and you will notice the pits getting bigger...then sadly cartilage starts to leak out of the holes at this stage I'm afraid it is too late.
I think the main problem here is an intestinal parasite infestation.
This is what I would do...
A mixture of Interpet No:9 anti-Internal bacterial and protozin. At the dosage of full dose of both on day one, half a dose of both on days two and three. On day four full dose on both and you should find this has solved the problem.
Yes the meds can be used together safely, it's a good combination and it works!
If you feed your fish live or frozen food, don't forget to worm them regularly, I use discus plus (good stuff).
For the HITH leave it a couple of weeks an do another course of Octozin, you may be able to close some of the smaller holes. If not I wouldn't worry too much...you fish will be free from stress and in good health so it shouldn't get any worse. I have read a couple of interesting articles that feeding earthworms can completely reverse the effects of HITH.
Garlic is a natural way of keeping your fish free from parasites, I squeeze 2 garlic capsules into my tank once a week, seems to work.

Anita