You say the water is *hazy* so no obvious particles?
Is this is a fully cycled tank? In a fully cycled tank that size you should be able to change 50-65% or more weekly without an issue. Have you added anything new to the tank that could be causing this?
I can't speak to a wet/dry filter system as I know nothing about it. In my tanks with HOB
filtration I would be taking apart the filter, using old tank water to rinse/clean all *permanent* or *semi-permanent* media and the filter box & tubing as well as replacing all temporary media(floss).