New liner, new opening - bottom of pool covered in white/gray dust - clouds

[JD880]

Hi, wanted to see if someone may recognize what this is. Had a new vinyl liner put in at the end of last season and it was immediately closed for the season by the pool company, I didn't do the closing like usual so I am unsure of what chemicals they may have used.

I opened the pool this season (had 2 covers on so nothing got in) and see this white/gray what appears to be powder along the ENTIRE bottom of the pool. I brushed some areas of it and it immediately clouded up the entire pool. Have had the filter running for 3 days straight (DE filter) and all my chemicals & readings are good. The stuff pretty much settles back down and is not getting filtered. Pool robot isn't picking it up either. Posted some photos of best I could including my skimmer sock. Any ideas on what this stuff is? Thanks!

 

[Texas Splash]

The sock seems to provide the best view, but even then it's tough to tell. Even though it's a new liner (and water), it could be just about anything. Hopefully not some old DE blowing back into the pool. For now, you might do an Overnight Chlorine Loss Test just to rule out the algae scenario. Once that's cleared, you might go into the filter to see if anything became damaged or loose.