First lets discuss the jumping. This can be due to many things and normally requires a hands on exam to find the cause. The most common reasons for this to occur suddenly are
* Injury to a disc in the neck or back. This can happen from something simple like jumping off the bed. Compression of a disc, disc herniation, or degeneration in the spine can all be the cause.
* Arthritis in the hips, spine or hind legs
For this I would suggest restricting her activity for the next 10 days, no jumping off the bed/couch etc, no stairs ( carry her if needed) no long walks and no rough play. She should be up to potty only and then resting.
It may be a good idea to get her started on a glucosamine and Omega fatty acid supplement. One good product that is available at pet stores is called Synovi G3 LINK
As for the yeast, this could be associated with the food she is eating.
It is never good to switch up the diet as this can cause not only digestive issues but it can make it difficult to ascertain if there is a sensitivity to a food.
Often increased yeast production is associated with sensitivity to grains or coloring in the food, however itchy feet and bottom are classic for protein allergies.
To reduce the yeast now I would bath the effected areas daily with Selson Blue Shampoo ( human). I would also get an e collar. If she continues to lick the problem will not go away.
I would start with changing to a grain free limited ingredient diet. There are a few available at the grocery store but you want to stick with one kind. Iams has a limited ingredient fish and potato, a cheaper one that I know some people are using is the new limited grain free OleRoy. I prefer a higher quality food such as Natural Balance duck or Bison formula but it is more expensive and has to be purchased at a pet store.
I would use a food that is grain free and has no beef chicken or lamb.
I think if you use the shampoo and the e collar this will help with the current infection and changing the food will have a long term effect.
If after the rest period she is still having trouble jumping or the problem gets worse then I would have her seen by your vet for a hands on exam.
Please reply back if you have additional questions or concerns and I will be happy to continue.