depending on the breeds of chickens that you have and there age, the issue may be one of many possible things. i myself am not an expert by any means and dont really know what help my advice would be but, i personally would ensure that there house is completely disinfected and cleaned every day for atleast the next week or two, that you stop feeing them vegetables as too much can cause upset stomachs, etc and ensure that they have been wormed. However this all depends on the age and breed of the bird, so i cannot give an accurate piece of advice yet, however i would continue with the medication that has been prescribed, as it probably wont make things worse. Also no matter what the bird is suffering from heat normally helps the bird to recover, as less of the birds energy is being used into keeping the body warm.