All right, again, I need to know what kind of mantainence you do.
Drinking water isn't necessarry for fish tanks, tap water is usually fine for them. However, the water is not fine once your fish urinate and deficate in it. Most notibly, fish produce a chemical called ammonia through natural processes. Ammonia is toxic and harmful to fish. Ammonia is convirted into another chemical called nitrite when a bacterial colony forms which performs the conversion (although the level of ammonia is already lethal by the time that colony forms). Nitrite is also toxic to fish, however, another bacteria colony forms to convert nitrite into a chemical called nitrate, this process usually takes 3-6 weeks in unseeded tanks. Nitrate is not nearly harmful but does need to be removed through weekly *partial* water changes. The frequency and amount of water removed depends on the amount of nitrate in the tank. The goal is to keep it below 20ppm. There are some tools that you will need to know the *exact* levels off all three chemicals in order to help your fish. You can buy test kits at the fish store to test for these 3 chemicals and these test kits are *invaluable* when it comes to successfully keeping fish in aquariums. Cycling is the process I explained above involving the developement of the bacteria; they are commonly refered to as the nitrifying bacteria. Also, ammonia and nitrite should always read 0ppm in a cycled aquarium.
The flaking sounds like a disease known as Ich, do a google image search to see if that's the case. The frayed fins are likely a result of finrot. I suspect that both were indirectly caused by and uncycled tank. You can find out your levels right now with out buying kits if you take a sample of your water to your fish store, they'll usually test it for you. If you do have ammonia or nitrite levels, do daily to twice daily 50% water changes until they are consistently 0ppm.
A side note, bala sharks get to big and spazy for a 60g (when they get older they smash into the tank walls and other unpleasant stuff).
HTH