How old are they? Reproductive problems including cancers, infections and internal laying, are not uncommon, particularly in breeds that lay lots of eggs (sex links are in that group). Birds over the age of two are where it most commonly hits. A swollen abdomen and stopping laying are often the most common symptoms. If the abdomen feels full of fluid, water balloon like, that is usually ascites, an indication that the liver is not doing well and leaking fluid into the abdomen, and it's a symptom of another underlying condition. If it's very hard/firm that can indicate salpingitis or internal laying and a build up of infectious matter in the abdomen. A very fat bird can have a large abdomen and will feel similar to ascites, but a bit mushier. Hard to explain, but it does feel a bit different. And a fat bird can have plenty of health problems. For ascites, also called water belly, some will drain the fluid and it will provide the bird some relief and make them more comfortable for a time. It's a temporary thing since the underlying condition will still be there and the ascites will likely recurr at some point. It does carry some risk of infection or shock, but many have done it successfully. There are videos on youtube showing how it's done. Most reproductive problems have few treatment options and most are not successful. If vet care is an option for you they may be able to help narrow it down. I've had birds live for up to 18 months with some reproductive issues, some passed much more quickly. It's very hard to predict survival times and often the definite answer as to what was going on is not known until necropsy. When mine get like this I leave them with the flock as long as they are eating and drinking and behaving like a (mostly) normal chicken. Once they go off food or water, act lethargic, isolate themselves, get attacked by flock mates, or are obviously feeling unwell, then I euthanize.