If it's been like that for two weeks without molting, it may be having problems because of a lack of iodine, as polkadotsmom suggested.
Instead of treating with salt, give it a bit of nori to feast on (your other fish will enjoy it, as well). It's the seaweed used to wrap sushi. My grocery store has it in the Asian aisle.
It not only has a good amount of iodine (the Japanese don't need iodized salt because they have so many sea vegetables in their diet), but a bunch of other nutrients as well. One bag will last you forever if you only use it to feed your fish. Slightly less than forever if you also make miso soup and other dishes with it.
