Hayward cartridge filter blow by?

I have a 24' AG pool with a Hayward ASL Series C1250 cartridge filter. I had a very bad algae bloom when I first opened it, but have gotten that under control. Everything is in balance and I have been maintaining a shock level for a week now and running the pump 24/7, but the water won't clear up. I replaced the cartridge with a Pleatco three days ago and it has gotten slightly better as I can just make out the bottom of the pool now. It seemed odd that it hadn't cleared by now so i dropped a couple tablespoons of cyanuric acid into the skimmer. Low and behold I saw crystals of the acid coming out of the return. It seemed to me that the filter should have stopped them. Can anyone offer any insight?

An update to my original post, just in case someone ever is looking for something like this...

It turns out, after looking around some, I discovered that the Pleatco filter was not the exact match as I was sold on. I saw a couple of things about the size but it seemed to be about the diameter of the cartridge which I didn't think would affect the way it mounted in the housing. When researching about it I found that a couple others mentioned their soft rubber end caps. The Pleatco has hard plastic ends. I have access to a water jet cutter and cut two gaskets for the top and bottom of the filter out of a closed cell rubber and it did the trick. The filter is running as good as ever. Mind you, this is the last Pleatco I buy...

Thanks for the feedback.

We've been recommending Filbur, Unicel, or genuine OEM cartridges (often made by either Filbur or Unicel!). The information we have received is that Asian made cartridges + Pleatco cartridges have lower over-all quality. So, it's nice to get further confirmation.