Rabbit breathing and stuck out leg

Not sure on her breed exactly..
   
Hi, I have a bunny who is sick. I went to the vet and they gave did x-rays. The women said there might be something wrong with her lungs. Like fluid or a tumor. Another problem, which I believe is not too severe is one of her hind legs. Something about her pelvic. The women was not able to give us more information so she recommended someone else. We went to him today and he believes it is Thymoma. He gave us some predinsone to use for awhile. We will do an Ultrasound next Monday. Also, he said her leg is like that because of arthritis but was not sure because he said she was a little young for it. She can run fine, still eats, poops, pees. I think she is not drinking enough water though.
   
Anyway her symptoms:
   
Breathing very heavy. Sometimes mouth is open and she looks up like there is not enough air. Started 2 weeks ago. Poop does seem harder and smaller than usual and makes a sneeze like noise once in awhile. Also, is not as hyper as usual. Not really sluggish though..just not all jumpy like usual..
   
I hope you can help my bunny..she means a lot to me :(
   
I'm just asking to get another opinion.
   
Here are photos and videos of bunny attached in zip file:
   
http://www.mediafire.com/?ol4aygqwryiof03

The symptoms are consistent with thymoma, but of course that is not a guarantee that this is your rabbit's problem.
   
If you are not satisfied with the second vet's opinion then you are certainly within your rights to seek the opinion of a third (I discount the first one since she referred you to the second when she came up blank).
   
Some vets are more well-versed in rabbits than others so be sure to ask about the vet's experience and expertise with rabbits before making the appointment.
   
Good luck, hope this all works out.

Thanks and me too.