Browning Montipora- why?

Any idea to why my Montipora is brown in the center? It was like that a month ago when I bought it (Cheap!), but I thought it would be better by now.



What is browning caused by? I don't believe I have any pests, so could it be excessive/inadequate lighting?



It is extended, but I am still worried. (I will take it off the frag rack soon, this was just temporary acclimation) (I slowly move it higher toward the lighting)



(The Montipora on the Left)







P.S: Can someone ID this monty? I have no clue what it is....