I have a similar issue currently with only my yuma's. SPS, LPS, as well as zoas and clover corals are happy and growing... while 3 of my yumas start dying off (look like yours).
This corresponds to 1) vibrant dosing and an almost complete absence of Nitrate and PO4 so I started dosing; 2) Of course the corresponding Dino outbreak; 3) increase of temp from 79 to 81.5F (summer)...
Any of this happening to you ?
For me I hope I don't lose any more as I have been specifically been collecting yumas and my collection is getting hit hard....
Hope yours recovers. Good luck.