Large sps colony dying from the bottom?

[Animal-Chin]

hmmm maybe. Would this cause the tissue to go from green/pink one day to pure white from the bottom of the coral to the top of some branches in 1 day though? I was cutting off entire dead branches of the coral that were totally healthy the day before. I've never seen anything like it. I'm googling and finding people talking about Rapid Tissue N somethingorother but no one really seems to really understand whats happening. I'm reading alk, I'm reading temp, I'm reading light...lol

So ya, like everything else in reef keeping its a mystery. I'll have to test the heck out of everything tonight.