well, my friend
i dont like saying this kinda stuff but here i go
a regal tang (Paracanthurus hepatus) will get up to 12"
and the clown fosh can get up to 4", unless you have maroon's which can get up to 6"
the damsels can get anywhere from 2"-5" depending on the type
the chromis's can get 3"-5" depending on the type
taking the smaller sizeed fish and the tang you are going to be around 39 inches of fish, and you have around a 50g tank
these might be ok if the tank was empty (just water) but rock and substrate will take some water out of your system, after all is said and done you might have around 35 to 40 gallons of water in there
what to think about when buying fish is, 1" of adult size per gallon, which is ok, but you have to also think about the swimming room also, and tangs do need swimming room
then you need to think about the personality of the fish, most of you fish can be a bit agressive and will show up even more when they are more fish in the tank than room
im not trying to hurt your feelings but you need to know this, we all have our learning curves, dont worry you are in the right place, i will let what i said to sink in for a bit, but you might need to get some fish out of the tank instead of adding more, sorry
TD