You should consider putting flow control valves on each line (or at least the shallow ones). You have diffusers at such different depths that your most shallow ones will boil like crazy while your deep ones will be more lack luster. This way you can choke back the shallow diffusers which forces more air to the deep ones. I put valves on all of mine so that I can shut off the deep ones in the winter.

And, a pressure gauge is very handy. It's a very good trouble shooting tool and I use mine to set up my one diffuser for wintertime.

Fish on!,
Noel