isn't this a newly set up tank? your tank is still finishing its cycling. you may be getting cyano and other nuisance algae because of phosphates if you didnt use RO/DI water.

when brain corals turn white, that sometimes means too much light and it sometimes means not enough. if it is turning white in the spot where it gets the most light, move it down, away from the light. if it is turning white all over, then it probably not getting enough light to sustain its hosted algae (xoxanthelli - sp?), so if you move it into more light, it should color back up.

the maze brain - it may just be changing color, i have had them do that, but if the tissue is getting mushy in those brown spots, it sounds like brown jelly disease, which i believe is a bacterial infection that spreads after some sort of injury - maybe a rock fell on it or something.

the acro may be browning out as a response to being moved into your tank. if it still has polyps out and the tissue isn't sloughing off, i would leave it alone and give it time to color up.