Every time we have a decent swimmer load in the pool, the water afterwards is cloudy.

I have made sure the pool is clean & all chemicals are ok beforehand. I can vacuum the entire pool or even brush all walls & the floor of the pool before everyone swims. The water ALWAYS goes from crystal clear to cloudy after everyone finishes swimming.

It always clears up overnight with no problems.

What could be causing this?

Before anyone asks...The chem levels before swimming last time were: (using PS233)

CYA...<20 (filled tube to 20 mark but could still barely see dot at bottom)
FC...3
CC...0
TC...3
Alk...110
CaHard...90