Sorry for the loss of your angel , those carry a difficult , advanced tag for most aquairists . They also tend to carry a poor survival rate if I remember correctly .. I am not real well versed on tangs but will do my best ..
I looked at your site but I saw nothing that indicated answers to my questions of size of your tank and the parameters . I did note that your SPG seems to swing a lot and quite a bit that needs to be stabilized at 1.024-1.025 .. What is the tank temp ?
I am going to go at this kind of what may seem harsh .. You have a mix of aggressive fish in a tank that looks no bigger than a 30 gallon cube .
The rock looks like it is not live rock either ? Was it dry when you put it in ? Did you put any rock that was called LR
in ? There doesn't look to be any beneficial algae on the LR
for the tang.
Ok now on to the rest , lets start this from beginning . Pick the 3 fish you want to keep IE The anthias , the tang and the occilaris clown fish . Those 3 should be fine together as they are all mostly peaceful fish you could add another anthias or even occ clown to mate up with the one you have, or even a few chromis to school ,the trigger ,tomato clown ,and any other aggressive fish need to go ...
The color of the tang looks normal as well .. Our LFS
has one in their display that is that color
Feeding the Tang you should use a seaweed / with a clip and place a small piece 2X2 in that clip if you can get him eating that . As for the clown and the anthias try getting 2 things one is called selcon and the other is called garlic extreme . You can use just regular garlic from your market too, just take one clove and a couple drops of your tanks water take a spoon and smooch the garlic place your food in it and soak it in the water/garlic for a few minutes then drop it in to the tank .. Mysis and pelleted foods are good choices and are fine to feed feed sparingly and only a couple times a week to prevent fouling of your water .You may also wish to add some more cured LR
to your tank as well to boost some biological filtration .Other wise your set up looks clean and nice .