Can't say for OP, but I'm seeing regression of a few cap monti's and also a spongodes, despite everything else looking great, and I think you may have hit the nail on the head. I am in the midst of slowly increasing time on T5s I recently added to LEDs. PAR toward the top of the tank is well over 300 with the T5s on. The acros absolutely love it; I was wondering if excess light might be the issue for some of those monti's.Any idea what the PAR levels are at in those areas? Since you mentioned SPS, I'm guessing your lighting is fairly strong; my monti caps start to die off (in the same manner) right around 250 PAR but are fine at just about anything below that (double digits low even). Something to investigate if everything looks good.