Nothing to worry about, the white blob will drop off within the next few days, its nothing more than a damaged denticle, basically dead tissue which no longer has a blood supply, such tissue develops fungus and becomes dislodged before being shed, no need to treat, it won't spread.
The other odd patch is nothing either, this too will disappear, nothing more than a rub or a rasp from something, make sure you don't have any Plecs sucking on the ray at night.
The eyes are bright, all in all the ray looks healthy to me.
Beautiful ray by the way.