Prazi for sure, when everything stabilizes.
I don't mean to add an extra problem here, but your tank is way too small for rays. Any ray, I would say min would be 100 gallons, and if I did put stingrays in that it would keep me up at night. Even small rays need a good footprint and a HUGE amount of water volume; I would go 180 if you had to stay smaller, but if you can't do that get as close as you can. ~250 would be better... depends on the type of ray.
I would do significant (conditioned) water changes and move them to a bigger tank. Good subsrate, good tankmates and a healthy feeding schedule should give you a much better chance at having your little ones pull through.
Hope I was helpful,
-Matt