Good looking rays. What size are they, and did you get a male, and a female? Looks like we got a rays about the same time, and they appear to be about the same size. It will be neat to see your updates as I watch mine grow also.
I was able "trick" them into eating some frozen bloodworms today. I mixed 1 cube of frozen bloodworms with the same amount of live blackworms, they ravaged the food so quick, only a couple bloodworms were left after they were done. That might work for you also?
Since I'm also new to this, I can't answer your question about the smaller one being inactive, but my larger one is kinda similar, but she's fat and healthy.
Can't wait for more updates! Cheers!