I had something interesting happen with the pool last weekend.
We had a few kids over for a swim. My son noticed that the force from the returns was weak, but I didn't think much of it. A few minutes later I noticed the waterfall had stopped flowing due to one of the kids holding the weir on the skimmer, effectively choking the pool pump.
Soon after she released the weir the pump primed and the pool went cloudy.
My wife noticed the water from the returns was WHITE - it looked like milk was coming out of them! A few moments later everything went back to normal.
The day before I had added about 7lbs of baking soda to get the alkalinity up. I mixed about 3.5 lbs at a time with 5gal of pool water, mixed it into a slurry and dumped it in the pool. Is it possible that I put too much in at once and it built up in the plumbing , constipating the pool? I think the abrupt on/off of the water may have cleared the pipes.
I tested the water after this episode and everything checked out normal - including the elevated alkalinity I was looking for and everything as been normal ever since.
This pool is entertaining in way I'd never imagined.