Sorry for the awkwardly worded title, I couldn't really describe the issue in one sentence.
My shower has a handle that controls both pressure and temperature. To begin showering, I turn the handle, then pull up the stopper (is this the right word?) on the tub faucet to get the water to come out the shower head instead of the tub faucet.
For the first few weeks, when I was done showering, I'd simply turn the pressure/temperature handle, the shower would turn off, and the stopper would immediately drop, letting out the remaining water through the tub faucet.
Now, however, it takes a good 10 - 15 seconds between turning the handle and the stopper dropping. It's not a huge deal on it's own, but I also notice that the water never fully transfers to shower-head-only when I pull up the stopper, and some continues to come out of the tub faucet.
I think it's affecting the pressure of my shower and it's just annoying. Any idea on how to fix it?