You may not believe this, but I found this out by accident...
I was using a turkey baster as I had a dragon goby that kept making a mess of things, he has since swam into my overflow so I flushed him into the refugium, so no more mess...
But during this time, where I had to clean the rock daily, over time my couple mushrooms in one area are now like 12, another area has multiplied also.
There is no scientific evidence, but the larger direct flow of water over the mushrooms may of made them split, or something.
Try it, if you want, let us know if it worked for you also