Monti Cap turned to a white bubble

[Ziggy17]

So I’ve had a periwinkle Monti cap frag since end of Feb. bought it with a red Monti cap. All seemed to be well in the frag rack along with the older and larger Montis in/on the rack. About 2 weeks ago, I noticed that the Periwinkle’s tissue was missing all around the perimeter, and the red Monti has a bit missing as well, nowhere near as bad though. I left it alone in hopes it would start healing itself, but day after day I noticed the tissue receding more, but just on the periwinkle. I did some research and thought maybe it was Monti nudis going after them. So i basted them off a couple times a day, looked underneath them, but found nothing. After setting my alarm a couple nights ant 2am, I went down with my phone to shine a light and see if I would catch the culprit(s). No pests, but I did have a snail circling anround the frag plug hole and the shell scraping the Monti. I’m gathering this is what caused the initial damage and it would explain the perfect circle of tissue damage on the frag. After the tissue receded to about the size of a nickel, I dipped it in coral md hoping it would help, but it kept receding. I decided to put it lower on the rock work to see if lower light would help it back. Well I woke up yesterday morning and the remaining tissue was a white bubble jelly. See photos. None of the other Montis were affected and the other that got damaged has been since healing.
See photos.
So I’m curious if the snail really could have done that, and do they all turn to white jelly when they die likE that?

Water parameters
SG 1.026
PO4- .1-.13
NO3 10-13
Alk 8.9
PH 8.31
Temp 77.5
Mag 1380-1390
Calc 450-470

Tank has been up for a year and water parameters have been locked in at those numbers for months. Stabilized. I dose 3cc of alk daily and 3cc of iodine weekly. Cheers

 

[isaacfish]

I noticed you have a flame angel those have a high chance of eating coral and also what kind of snail is it that would be the difference between snails and destructive power

 

[Ziggy17]

The flame is a model citizen. Haven’t seen it nip a coral ever. Just bugs the Anthias once and awhile.

It was a astrea snail. But I would have thought all snail shells are basically the same.