My bet is that you are having ammonia or Nitrite problems. 99% of the time if they are floating and not acting normal that is the problem.
My motoro would also do the same thing every so often. I not sure why he does it but it does like to play in the air bubble curtain.JohnG;4682190; said:1 of my larger motoros likes to do this sometimes, I will find her floating around just like that for hours at a time. Never seen any of the other rays in there with her do it and I have a oxygen pump and a waterfall airating the water so I doubt its an oxygen issue in my case. I have seen her doing this for 2 or 3 months now and she is fine, hopefully yours is ok.
And like rkiranking said, use something to declorinate your water, if your getting a bunch of strange behavior right after a water change that would be the most likely cause.
I use salt with my rays all the time, never had an issue. The only thing is you want to disolve it first or put it in the sump as direct contact with undesolved salt can injure them.