Hollywood stunner coral white

I recently received an hollywood stunner that someone owned for 6 years. I put the stunner in my tank and the first 2 weeks it was Brite green. At the beginning of the third week I began getting partial white slime on it. Over the next week this white slime began to get stuck on my coral and now it turned all white within the week. All my fish died during this time exept 2 fire fish not sure if it was due to my kh being high, my hand coral dying or if it was this stunner coral Help my water is fine temp is fine. I cant scrub white stuff off my coral sn now it spreading to my rocks

Attached Thumbnails