ERGENT FISH QUESTION!!!!!!!?

I have a 36g gallon tank with two Discus(young 2-3"), six tetras, two snails, and two(2") bala-sharks(only until they outgrow my tank then I have a friend who will take them), & two dwarf gourami's(1 1/2"). They all were doing wonderful together! Until 1 of my tetras got ich, I treated it seemed to be gone, but is now back and has spread to 1 bala, 2gourami's and the same tetra! I am treating again. Now my Discus are acting different. One has become dominant, it isn't letting the other eat, and will chase it around the tank. How do I stop all of this? Oh! I'm looking at my tank and realized my ammonia is higher than usual! WHAT HAPPENED!? How do I bring it down?