Recently I've had the same issue with the same type of dieoff, needless to say it was the rodi issue. Growth in some acros stops completely, some acros get burnt tips, or stn from the base, other acros are growing and have the nicest PE, that's what I've observed. (Red dragon is usually the first one to leave the party when you have the rodi issue, or chloramine then go birdsnest) funny thing is Vivid had the same issue in their tank and their corals reacted exactly like mine, down to the space invader pectinia, surprisingly that coral gets burnt tips too. Someone told me that my RODI was the issue when the problems started, but of course I'm the smartest guy around and I ruled that out immediately, checked my tds it was at O, and went on chasing ghosts for a while, bacteria, ph, alkalinity, light, you name it. After going a full circle of course , a buddy of mine told me to put some prime in you topoff water or any w/c water. I found it to be a great test for this type of issue. As soon as I put some prime in my topoff the stn stopped. The corals still looked somewhat crappy but I can see that the corals no longer stn at night, and the burnt tips didn't recede further. That's where I knew I had to replace all of my filters. After replacing filters and doing a large water change with some new water. All of the corals began to recover. 2 brs chloramine blocks and 2 di filters cost about as much as one triton test. Hope you have the same issue so you can fix it quickly.