Aw, poor bunny.
A lot of times when one thing goes wrong their little bodies get stressed, their immune systems don't work well and that allows other things to go wrong. They may have a bug or 'germ' in their system that's kept in check by their body's natural defenses, but the defenses are down when they're not feeling well and the bugs/germs can multiply.
Was she having trouble in both legs or just one? Was the medicine you got Metacam? She may be feeling poorly again with the arthritis or whatever it is and that has caused a respiratory bug to take hold. Or it could be something else entirely.
If you can't go to a vet, best thing is to keep her comfortable and eating as many healthy veggies and hay as a possible, and try and get her good quality timothy pellets (and don't give her too many of them).
Could she be much older than four? How is her weight? She looks chubby in her pictures. (Sorry Bentley!) Is she getting fatter or thinner? Rexes tend to get a little too fat and the extra weight puts more pressure on their legs and joints which can cause any pain to increase. She's also getting less exercise so that may not help her weight, either.
If she is overweight, you don't want her losing weight quickly, but you do want to get her to a healthy weight with decent veggies, hay and quality low-protein, low fat pellets.
On the other hand, if she's already losing weight, you don't want to cut back on the protein, so its important to observe that. You can't go wrong with a wide variety of vegetables (which will give her different kinds of vitamins), a few pellets and a lot of hay, though.
Its unusual she's turning down a banana chip, isn't it? She really shouldn't have more than a tiny bit of it anyway, but whenever they turn down a treat around here, its cause for concern. Is she is quieter than usual?
Bunnies really do hide their illnesses. By the time they're showing symptoms, they're pretty sick.
She really does need an exam and probably an anti-biotic, and it would be good to see if she should get more Metacam if that's what you have.
sas
ray: