Like I said, "IF" it was me. I say this cause I tested my water parapeters all day long after loosing the first ray in my recent dealings with sick rays.... The parameters were fine. Ray died and another one started showing similar symptoms. I had 2 choices, either re-assure myself my water was fine, OR assume the test kit is irrelevent and my water was crap. Well 2 days after making the decision of "my water is crap" the ray that refused food for 5 days is packing on weight. Was it the Binox or the waterchanges I can't say for sure..... But the Binox was added at the 1st sign of the 1st ray getting sick. 2 days in she died. 2 more days go by and the 2nd ray begins refusing food. This is when I began with WCs.... AT least once a day and readministering the Binox.
Maybe it's nothing. Maybe it's just a little irritated, maybe it IS something. Hard to say without seeing it in person, but as a person that has lost Marbles I know I would be taking some kind of action.
Just my opinion.... IF your ray was allready established your water would be "fine" but since it's obviously went through a rediculous amount of stress lately, and is not only new to captivity, but new to you and that tank as well nothing shy of PERFECT water is going to be "fine".
Please understand I am just trying to help.
I'm assuming you allready have her seperated from the other rays and have allready tried live ghost shrimp?