I would buy CO2 specific check valves, I like brass/stainless steal ones. However, the ones used for air you can buy at any pet store work fine, they degrade over time. I would buy them for a quick fix and order some nice ones in the near future.
You can check for leaks after the regulator by just putting everything under water. If you have enough slack in you lines, you can put your bubble counter under water in a cup or small pitcher. If you see bubbles, you have a leak. My diffusers make noise though that could sound like a leak. Not all do, one of mine is actually quite loud. It could sound like a leak if I didn't know it made noise on it's own.
Oh, that's reassuring. There isn't a leak, I can tell you that much, and I will just do regular check valves until I can get some nice fancy ones. And yah, I think I know part of my problem now......me being afraid to OD on anything only put the working pressure at 10.....I mean it was bubbling and all.....but then I realized that it was supposed to be at 36 for my atomizer anyways, s I feel kinda silly about that now.
I just need to get some check valves for now, then I was told that at 36-40 pressure that all the mineral oil in my line that shouldn't be there will blow out......so I think I'm good to go.
I'll update later once I have this all working properly.