Keeps getting cloudy - Please help...

[myLABSpool]

I have a 24K IG vinyl pool. I maintain the water between 81-85 degree and I watch my chems closely and I still have problems with my pool turning a milky cloudy. I shock with liquid before it gets so cloudy that you can not see the drains, but this propensity to require shocking is getting to be really annoying and makes me wonder if there is something wrong with either my filter or other unidentified water problem.

My numbers (based on my Taylor test kit)
FC 3-6 depending on when I test and add more. When I shock I run it to 12ppm based on my level of cya.
CC - 0
pH 7.5
TA 100
CYA 30
Calcium low, but it's vinyl so this should not matter, right?
Water temp 81-85
I have no sign of algae.
I only use liquid CL, but I did use some pucks until my CYA climbed up from 15 at the beginning of the season.
I do keep the pool covered with the solar blanket when not in use or not at shock level.

I use skimmer socks and I have a sand filter and I do use DE in my filter which seems to help clear things up, but I'm stuck in this cycle of cloudy, shock, clear, cloudy, shock, clear. I'm beginning rue the day that I made the decision to go with a sand filter because I almost went with DE or cartridge instead. When I was a kid I had a DE filter at my parents and I was in charge of maintaining the pool and I never had water problems. My neighbors have cartridge and don't have as much cloudy problems as I do. I am replacing my sand this weekend and I made the investment in Zeo to see if that helps.

Any other suggestions would be appreciated?