Red retics usually come in VERY thin, I would treat for parasites ASAP! Prazi is good, Ive even direct injected the rays food items with prazi pro.
Plus its cheap so why risk it? Rays, being bottom feeders, are naturally a host to many parastites. In the wild this is normal and the ray is fine. In captivity, a rays immune system will be subdued allowing an parasite to cause possible harm to the ray.