Hi everyone. I'm a newbie here and to pools in general. We installed an above ground pool last summer and it's been trouble free until recently. I realize that one of the prerequisites here is to have a good testing kit. Unfortunately I've only been using those test strips. Maybe out of dumb luck my pool water has been sparkling clean until recently when I cleaned the cartridge filter about 2 weeks ago. This was the third time I cleaned the filter this season. The past two times, there were no problems. This time, I noticed that when I turned the pump back on after cleaning the filter, a bunch of grey-ish water came out of the return. I'm guessing it's the water that was in the filter housing. I figured that the filter would clean it up but ever since then, the water in the pool has been a bit murky. Before I was able to see straight to the bottom, now I have to strain my eyes to see it. I've added a bit more algaecide and super clarifier to no avail. I've even replaced the cartridge filter with a brand new one, but barely a change. The water is not green, it's just murky, grey-ish. According to the testing strip, all levels are ok, including free chlorine. In fact, per the strips, the balance has been very steady for ph, alkalinity, free chlorine, stabilizer, etc. Any suggestions?