Pretty much agree with what Avatar's advice. I wouldn't exactly say that replacing cartridges is wrong, a lot of people are perfectly happy with that approach. But ime the next step in the learning curve is to use filter media permanently and rinse it out periodically rather than replacing it, (an exception would be carbon, if you're relying on it for chemical filtration, but even carbon becomes a bio-media after a while since your beneficial bacteria basically colonizes any surface area in your filter).
If you think of your power filter as essentially a media chamber with a pump to push water through it, the pre-made cartridges are kind of a waste of your true media capacity. Since filter capacity is basically a function x volume of water flow through x volume of media and not
just water flow, imo you'd ideally want to fully use your media space instead of simply having a couple of wimpy cartridges. Here's an example:
Essentially I've more or less tripled my media capacity here compared to using a cartridge in the same space. Instead of cartridges you can use filter pad, poly filter floss, ceramic bio media, bulk, loose media in a mesh bag (like carbon, Seachem Purigen, etc.) or other options or combinations. If you notice I keep the original media frames in place simply to keep the poly material out of the bio wheels. You can keep using carbon in them or other loose media or cut filter pad or sponge strips to put in them. For filter maintenance I just alternately rinse out the media from one side or the other in a bucket with tank water as needed (not tap water, the chlorine kills your beneficial bacteria). The advantage over buying cartridges is it saves money, saves regularly throwing out half your beneficial bacteria colony, gives you more media options, and uses more of your filter's true media capacity.
I wouldn't guarantee this alone will solve your water clarity problem or that you may not need more filtration or larger water changes, since all of that varies with each setup, but you will definitely save $ and get more out of your filter ime.