Thank you for your responses!
My ammonia only seemed to rise after my fish had died, before that my ammonia was nonexistent. I'm hoping that's why it's showing up, how often should I change the water to eliminate ammonia?
I just wanted to start out with damsels because they're a much hardier and least expensive fish. I think the yellow tail was just stressed due to the ammonia the 4 stripe is doing well for being nipped so frequently. I will monitor my water parameters for 1 or 2 more weeks before i get rid of the damsels and replace them with something much more friendly.

Quick question though, should I start adding corals such as mushroom corals before adding new fish? I'm new to the hobby so any advise would be greatly appreciated!