Depends,,
Are they wild caught rays or captive bred? Are there tank mates? And if so, can those tank mates make the ray feel threatened or can they possibly pick on them?
Wild caught will usually take a bit longer to adapt to a new enviorment, they have to get used to life in captivity. If they're eating, there is no big worry. Keep up water changes. I can never expess this enough, water quality is the key with rays, even if you have crazy filtration, water changes, water changes, water changes.........unless you have an aquarium of silly proportions((1000gals+)) & lots of feeding and in no time you'll probably be pondering ways to keep 'em from splashing about.
P.S. welcome to the ray addiction