I have a hen who is healthy in all other respects and lays a large brown egg daily - she is a 2 year old Black Sex Link - but, she too filled with water and got so big she nearly died, couldn't walk. The first time I drained her I got a cup full of clear water out of her and she continued leaking on her own and soaked (sopping wet) two folded towel. After that, she was back to running around the farm. I had to drain her again in about 3 months (again clear fluid) but made sure I did it before she got too big. Then a third time in another 3 months that time slightly yellow watery fluid. Now it's been several months and I haven't had to drain her again. I have no idea what caused it but she's active and still lays daily.