one word, stress.
Pelvicachromis taeniatus comes from soft acid water and are not commonly bred in Asia. Therefore the fish or its parents are probably wild caught. The pH is way too high for the species to be happy in. You need to lower the pH to 7.6 or less. If you want to breed them then get the pH below 7.0.
If the original owner had them in alkaline water then that would explain why he couldn't breed them.
A pH of 8.6 will cause real problems with any uneaten food. As the food rots it produces ammonia and in a pH of 8.6 a tiny amount of ammonia would be extremely toxic and enough to kill most fish.
You also need a backing on the tank to reduce the stress, and I would put some plants in there, either plastic or real, it doesn't really matter.
Adding a few small peaceful tank mates (lemon tetras, cherry barbs, etc) is often a good way of getting fish to eat. When the newcomer sees the others eating, it will usually try the food, (ie: monkey see, monkey do).
Try feeding the fish on live brineshrimp or mozzie larvae. When it eats regularly then offer other types of food.
Stop using the copper medication and do small (10-15%) daily water changes with neutral to slightly alkaline (pH 7.0 - 7.6) water. Continue with the small water changes until the pH is at a more suitable level. If you have any calcium based rocks/ ornaments in the tank then remove them.
If the fish shows signs of ich, (actually has white spots on the body) then treat if, but otherwise don't use any more medication. The combination of high pH and any trace of ammonia could well be why the fish was rubbing/ scratching. The highly toxic ammonia burns the skin and causes the irritation. Adding the medication could simply irritate and worsen the problem.