Are the bowls stainless steel? Some metals are very toxic to birds. You need to clean out the waters at least once a day. I scrub my budgies out every day with a bit of natural dish soap and a paper towel, rinse super good, and then usually rinse it out again in late afternoon/early evening. Be careful getting small animal bottles as they can be really hard to clean and build up bacteria very quickly. I think it's very possible that they could have got something from your chickens, everyone should be very, very careful to wash hands and clothing that has come into contact with poultry before touching anything our parrots will have access to. To be sure that the others are not sick, the best option would be to take them to a certified avian vet.
How old was the bird? What were they eating? What kind of living/housing situation were they in?
I hope I'm not sounding rude, just passionate about birds and trying to help