Gout can cause shortness of breath & breathing difficulty, along with pain in joints of the foot, legs & elsewhere. An overly high-protein diet and/or excessive use of antibiotics can contribute to the development of gout.
It doesn't really sound like either of your roosters have gout, but I...
I would check to see if either roo has had one of their Achilles tendons slip out of place in the hock joint. There is info on this & other leg problems on the Poultry Podiatry page on the site linked in my sig. I hope you can find the right treatments.