Freightliner cascadia secondary air Tank issue

I am having issue with secondary air tank pressure on my 2015 Freightliner cascadia. First it was holding air pressure for about good hour before it drops down to 100 psi and eventually air compressor kicks up and fills it back up. Then recently whenever I am going down on rough road it would last for about 20 mins. So I thought maybe I have a bad air bag and decided to fix all the air leaks and also changed all the air bags then so far so good. But yesterday going down the road secondary air gauge would go from 130 psi to about 125 psi in 2 mins and air compressor kicks in at 125 psi instead of going all the way to 100 psi. Then I stop to check and get back on the road and it’s fine again but it happens every now and then where secondary gauge drops down to 125 psi and air compressor kicks in especially on rough road. If anyone have an experience or suggestion on this issue would be greatly appreciated. I am going to take it to mechanic to get the turbo checked.