Stingray gowth, need some help

I have owned this stingray for about 2 years now, perhaps a little longer now that I think about it. I have had rays before, and have been in the hobby the last 10 years or so. I have a 13'' Motoro stingray fed a mix of shrimp, octopus, earthworm and krill. she is in a tank all by her lonesome (used to be with discus...that was a $300 mistake). Im actually in the process of setting her up in a 180G (still culturing) which is taking the better part of a few months to set up. The reason for this thread is to discus something I can't seem to find any information on. I've checked forums, books, and online sites to no avail, so hopefully someone can help me. A few months ago I noticed tiny spikes growing on her disc, very similar to the row of spikes that she already has on her tail. they look like white head pimples, at first i thought it was anchor worm but after research and other help i was able to determine it wasn't. they do not look like wounds, or sores but rather natural growth, and my experience has onnly been with juvie rays not much in terms of adult rays. I dont know if this is something natural like a defence (such as that on her tail) but there have been more of them, so it raises a concern. No one in the LFS or even the specialty stores can help me, so hopefully someone here can. I will try to post pictures, any help would be great. PH is at 7,Chloramine 0, ammonia .002, nitrate/nitrite 0PPM. water changes are twice weekly at 40%. I will check this post daily so that if their are any questions I can try to answer them as quickly as possible. thanks fo any help.

Hey there. thanks for all the replies. As for the tests I do have a mster test kit but in this instance I used a test strip ( i know.. i know) to be able to throw some numbers on here. The water is definatly a little harder then what I'd like, The new tank I am setting up I actually considered using the Fluval shrimp substrate to help to buffer/soften the water, but with all the movement of the ray I'm afraid it will just tear up the gravel and get stuck in the filters (any suggestions on gravel that can buffer/soften water?) its possible with the larger tank to put some driftwood in to help, but for her size i'd rather give her as much space as possible, i've also considered peat moss to help but not too knowledgeable on types/where i can get it/etc. My knowledge of ray species isn't the widest, and aside from my own, I've only ever seen a few in the LFS, but the colouring was always the same, how is the colouring unusual for mine? (always been this colour, not sure if should be a concern or just something natural or possibly the effect of the flash). I can post a full body shot in the next day or so for sure. new to the site, I have some friends with some monster fish that would love this site! Again, thanks for the help!