Came home to a slightly cloudy tank? Possible causes?

So went to work for about 3 hours and tank was crystal clear when i left. When i came home i noticed a slight cloudy tint to water. What could be the cause? I checked for any dead snails or hermits saw nothing. I only keep chaeto in my sump. This happened once before when my turbos were trying to spawn i saw them shooting what i assume is sperm into water column. But im at a loss im not sure, aby ideas? Nothing was near tank that clild have spilled, and im bare bottom so theres no way sand was disturbed.

Thanks