Our daughter's favorite chicken (out of 44) is sick. Please help me save her!

[Wyorp Rock]

 

[counterWULF]

OK, back again needing more help. We discovered one of our youngest egg-laying hens now has water belly. I wanted to find out if this might any way be connected so we can fix things before more and more start dropping. We have 3 generations of hens. The last one with water belly was 3 years old. This new one is only 1. Do a lot of chicken owners deal with water belly from hens of all ages? Is this from poor breeding? Our first 2 batches came in the mail. This youngest generation is from one of our hens and possibly 3 different roosters. So maybe there is some genetic connection through the hen or rooster line? Our 1st gen chickens came from a reputable breeder, but our 2nd year chickens did not. The first gen breeder accidentally allowed his website domain to expire and someone else snatched it up and we didn't realize it until it was too late and we purchased gen 2 from the bad breeder. We had plenty of issues with gen 2 chicks with crossbeak and other sicknesses early on. We were able to save most though. The dying runt from gen 2 is now our biggest fattest hen. Haha! Anyways, please let me know if we need to change or add anything to help prevent water belly in the rest of our egg layers. They all seem too young to be dying off like this. I thought their life expectancy was 5-7 years, and they are only 1-3 years old now.