Possible it could be fish TB. Fish try to eat but can't and spit as you said. Dropsy is hard to cure and usually indicates something more can be wrong. With all this said, raise water temp. (as long as you are sure the tank is cycled and no ammonia is present) to 80F. Feed shelled peas, antibiotic fish food, or fish food soaked with castor oil. These things help flush the fish out, but if it can't or won't eat it does no good. Use 1/8 tsp. of Epsom Salts per gallon of water. Epsom Salt is a natural laxitive and will flush the fish without him eating.