It is probably the diffuser needing to be cleaned. I have this regulator as well and I'm using a GLA atomic diffuser. My bubble rate slowed down as well but after I cleaned the diffuser the mist was finer and the bubble rate returned to normal. You might have to clean it really well using the acidity detergent if you have it. Use just enough to coat the outer surface and let it sit for 30 min, then do 50/50 bleach and water bath for a little bit and rinse in fresh water using a dechlorinator like Prime or whatever you typically use. Let it dry completely, which might take a while, and it should be good as new. I cleaned mine a couple times because it was really clogged but I was only using the acidity detergent and I didn't give it time to sit for 30 minutes. I contacted GLA about it and they gave me the more detailed cleaning instructions. Hope this helps.