HELP! What Is This?

[MaxC-130]

Last week, I bought a Trumpet / Candy Cane Coral frag from my LFS.
Yesterday, I noticed this lump developing.
Today it is twice the size!
Can anybody identify and advise, please?
It’s in an RSM C-130 and is placed on the bed under a cave to reduce light levels.
I have hermits and snails, clowns, damsels and cardinal with mushrooms, zoas and green star coral which are not affected but the Trumpet replaced a Xenia that died within a couple of days of being introduced to the tank two weeks ago.
My parameters are all good and the LFS conducted a thorough water test with no issues identified.

 

[DaveK]

Could you describe where in the photo the lump your talking about is?
The photo is a bit blurry, could you get a better picture? Sometimes it helps to brace the camera against something solid like a chair back.
Please post exact parameter readings. Statements like "My parameters are all good ..." do not tell us anything. What might seem ok to you might indicate a problem to someone else. Also we want to know what was tested.