| There is a book "The General Care and Maintenance of Bearded Dragons" avail through the Herp Shop which is excellent and I think a must for all beardie owners. The information I'm giving you is basicly from that book. Symptoms of calcium/vitamin D3 deficiency is tetanic twitching or the shakes, other symptoms may include neurological problems and soft jawbones. Treatment consists of supplementing the diet with a calcium/vitamin D3 supplement and exposing the animal to sunlight for at least 30 minutes daily. Respiratory infections when present, the most obvious symptoms are gaping, forced exhalation of air, puffing of the throat and a puffed up appearance of the body, treatment is keeping the animals at higher temeratures(book recommends 30.5 - 33.8C). Also dont interpret the normal gaping behavior of bearded dragons when they are overheated as a sign of respiratory infection.
Just keep in mind if they are inland/central breadies that coming from dry areas that they don't like high humidity so be careful with high temps and misting. Good luck, hope this information is helpful.  | 
