for a bunch of pro's you all ask alot of amateur questions. If all coral is well but one you should know the water if fine.
I don't think thats a good way to ask for help at all.
And no, all coral do not particularly like the same parameters, Coral all don;t come from the same place, most are collected OCEANS (thousands of miles) apart.... And ontop of that if you ask people what "Good" or "all parameters are fine" is for their tanks parameters i am sure you will get a range of answers. 1023-1027/8 on salinity, 400-480 calc. 7-11 on alk, temp from 74-82. I think those are big swings in parameters. So in sayign everything else if fine so the params are ok, it leads to either the colony is beeing bothered, it doesn;t like 1 parameter, or your putting it in the wrong spot. The fact that the acan looks like its high up in the tank is one thing your doing wrong and might be a reason why its not puffing up. also the fact that it was fragged and growing back is another. We have no idea how you got the frag, how long you had it, nothing.
Whats your calcium, PH, temp, hows flow, whats Po4, and any other parameter your testing for? hows everything else.
The question you asked was like asking someone why the car won't start without giving any other information. Could be no gas, could be bad spark plug, could be one of 1000 different things. Because your not getting an answer it means your not giving enough information.
So don't be a
smartass and say something about the people on the boards if they are kind enough to ask what they need in order to help you. next time post a pic when you first ask the question.