Sick ray - looks like bloody warts?

Two of my four flowers now appear to be having some sort of 'issue'. It started with them both lifting their discs, though nothing was initially visible. There now appears to be a bloody red 'rash' on the underside of their discs. I would have just thought a scrape of some kind that would heal, but with them lifting their discs first and this then appearing and now spreading, it is definitely an issue of some kind. It has spread on to the top of the gill on the female that has it, as well as on one of her spikes on her tail. I hope the pics can further show what I'm attempting to describe. The one on her gill and tail appear to be like a wart that's red underneath and an opaque whitish on the outside. I have no clue what this could be, but it definitely appears to be getting worse.

Any and all help/suggestions are appreciated! Temp has already been raised to 86 w salt added.

I don't know, it's really hard to say. The two with the issues on the disc were lifting their discs before there was any sign of anything. A day later the red areas appeared where they were lifting their discs and panic set in. Doesn't appear to be old wounds by any means, but I suppose could be.

I've had rays in this tank for almost 3 years now; a pair of motoros before switching to flowers almost two years ago (tank was new, rays were the first fish in it, with the same sand the entire time). These same 4 fish have been alone in the tank for almost two years until this past weekend when I had to put in a shoal of silver dollars for 3 days while I moved some other tanks around. I've had the silver dollars for over two years as well, with the the most recent addition to their tank having been 4 small red severums that were quarantined before being added 2 months ago.

I had put in some ceramic tiles to see how I liked that look of a black bottom about 2 months ago, but have now removed them fearing that they may have been the cause of this outbreak.

Other than that, nothing has changed with these fish, so I'm still wondering if it's a reaction the stress of the silver dollars for 3 days (the marks/wounds are definitely not bites).