This sounds like a respiratory disease in the second chicken, possibly MG or coryza, but infectious bronchitis can also be considered. Cornish cross meat birds can die of heart failure at an early age since they are meant to be processed after 6 weeks. Drugs such as Tylan and oxytetracycline can be used to treat symptoms of respiratory disease. Here is a good link to read about diseases: http://edis.ifas.ufl.edu/ps044
- Monkey Lookout
Not personally - i know that some BYCers add a little bleach (i.e. chlorine) to water, as it inhibits the build up of bacteria. All mains water contains a small amount of chlorine, so i don't bother - i just change their water regularly.