have Service Air Suspension message every 2 seconds

[dna]

Got a 03 H2 with the air suspension. Noticed that about 3 months ago that the H2 rear would be low if I left the truck alone for 24+ hours (like the air bags were leaking). But by hitting the raise button the truck would always lift again. Shortly afterwards I started to get Service Air Suspension oh-**** lights going off every once in a while. Now I get this message popping up every 2 seconds. The same issue exists - the truck will be low if now left for 12 hours but I always can raise it by the raise button.

So I suspect I have a leak somewhere. Does anyone know where or how to start to find the issue? If the bags are leaking, is there a way to fix them or will I need new ones?

Thanks