not developping

My four week old Easter Egger does not seem to be developing properly she’s very lazy seems to be lethargic and I’m not Sure if this is just part of laziness ....she eats she drinks my three other four week old chicks All have developed their wing feathers and their tailfeathers she still hasn’t...

I have some silkies ive been trying to hatch now for 2 months with no luck. The eggs are fertilised (bullseye) but yet do NOT develop in the incubator, I have 3 pullets and 2 roosters, all have been laying for a little over 4 months. I collect when the eggs are freshly laid and warm so its not...