Indoor Public Pool Turned Green and Cloudy

Question about a public indoor pool. The water quickly got a mustard green tint to it and can't see the bottom much within 2-3 weeks somewhat suddenly gotten worse. About 3-4 months ago the sand in the sand filter was changed out, we use Clorox clarifier once a week as well as a 6 in 1 Clorox Shock once a week with algae killer. Pool gets vacuumed once a month as well. Can't seem to pinpoint where to look for what's causing this issue. Ph, Bromine, and Alkalinity are all normal levels. Any and all tips would be appreciated thank you.