What’s up with my air pressure

Hi everyone. I have an East triaxle dump trailer air ride with a two liftable axles. Just recently the forward axle is not filling up all the way. Found a blown airbag which I replaced and also replaced one of the pilot valves. Still does not seem to be getting full pressure to the long down bags. Thee convoluted lift bags are working fine. Any ideas out there would be most appreciated. Also wondering if I have a bad check valve. Thanks all.