I believe this is a WC one from a vendor in B.C. and wasn't quarantined and treated for parasites before he bought it. It came in and went straight to his tank.
I learned the lesson the hard way about buying WC that aren't quarantined and treated and lost my first couple of rays. You did prazi so that should help, so now just keep the tank stable like skynoch said and water changes and good food! Try dew worms as my pups always ate those and it wasn't hard converting to smelt,shrimp and pellets after.
I received some good info and insight from some members here and probably will never buy a newly Wild caught ray ever again. Can't stand the stress and hassle! I have some WC Henlei but they were in a tank for over a year before I bought them!
Now that people are breeding black rays on a more regular basis you can always find hardy CB rays for good prices!
Goodluck.