That's one of the troubles of a centralized air system: it really only works if the tanks are all about the same depth. If you mix a couple of much deeper tanks in there, the pressure is higher, and air goes out through the place of least resistance...
I found this even on a system with 15s, 40s, and a few 65 highs. The 15s and 40s were similar enough in depth to not be an issue, but hit that deeper tank, and they just couldn't push. You can, of course, lift your airlines up (I had some of my sponge filters on multiple risers).
Even a bigger pump may not solve it -- you need extra capacity to compensate for the pressure differential.