Green poo means they are dehydrated and starved. I had a hen that died this way for no apparent reason; give them electrolytes (gatorade), yogurt to help with digestion, and mash their normal food with warm water to make it easier to eat. Keep them in a warm, dry place (preferably in the house so that you can watch them at all times). You can also give them tomatos and cut up grapes if they look like they could eat more. Protein is a good thing to give them, too. Although, I'm not sure it would be a good idea to give them bugs, since the bugs might be carrying whatever made them sick in the first place. Also, it may help to clean out their coop, hose it down, and let it dry, just to make sure that whatever your birds have isn't being spread through contact with the same shavings, hay, ect . . .
Hope your birds get through this!