Hmmmmm..... new brush is doing the exact same thing. I also ordered a puck of Mama Bear's Awakenings for something different to compare MWF to. I've used Awakenings many times before, and it is doing the exact same thing as MWF with both the old brush and the new. Lather is dry by the time it hits my face. It's pretty clear that the brush is not to blame.
The main suspect now is hard water. I haven't tested my water before as I haven't noticed a problem until now, so I won't be able to know if it's harder but a test kit should tell me how hard it is currently.
So here's my next question: I use an electric kettle to heat my water while I'm showering. Assuming the test does indicate I have hard water, does it seem like a good idea to add a little water softener to the kettle as it's heating up?