Just a couple of suggestions/observations for you.
Try to keep your hands out of the tank as much as possible - I know this is hard particularly when you are just starting out but do try. This could be what is stressing the coral
You have a sailfin tang in there, and as I am sure you know, your tank is way too small for this fish - they grow big and while yours might be small right now it will grow fast and you will have to have a larger system to properly house that fish. Another fish that you have is a Mandarin dragonette and it is generally thought that they will need a larger system with a lot of copepods, amphiphods etc. to properly feed them. I know that some do accept prepared food and if your does that is great. - Just an observation.
Another suggestion is to take a water sample into one of your LFS and have them test it for you. I know that with new reefkeepers it is pretty tempting to overfeed you tank and this can lead to high nitrite and nitrate. Been there done that
