HELP! Background: flock of 11, aged 11 to 4 years. All wormed in January. 4 hens have swollen abdomens, presenting with tails down and messy butts. All bathed in epson salt water to clean. All drinking adequately but eating less than normal. None are laying, 1 is too old to lay. 2 have very messy bottoms (the youngest and the oldest). I suspected vent greet or egg yolk peritonitis on the youngest one, but vent looks fine, feces looked very yellow. None of 4 seem egg bound. What could this be? My concern is it’s contagious since 4 out of the 11 seem affected. Any help would be appreciated...no vets available for chickens in my area.