When was the last time you checked your CYA level?

If your chlorine level has been dropping below the minimum needed, it could be that you actually have an impending algae bloom that is trying to get started. Why don't you go ahead and shock the pool this evening. Then, a couple hours later, test the FC and CC and then repeat those tests in the morning within an hour or sunrise. If you have lost more than 1ppm of FC overnight and have a CC reading greater than 0.5ppm, you'll know that you are losing chlorine due to fighting something in the water.

If you don't and you verify that your CYA actually is 50-55, then it may be that you might want to consider raising it a little higher. Where do you live? Some people who live in some really hot parts of the country find that running a higher CYA pool allows them to test and add bleach less frequently. If you have a lot of rain, it can lower chlorine some but not tremendously. In my pool, a lot of rain affects my pH more than my chlorine --- lowers my pH.

After writing my reply, I scrolled back through your thread. Did you ever order a K2006? If not, you won't be able to measure CC.

Are you aerating the pool? Is your return jet eyeball aimed upward to create splashing on the surface? That can cause pH to rise. How high was the chlorine when you tested pH. With kits other than Taylor, the pH test will be inaccurate if the chlorine is higher than 5ppm. (With the Taylor kits, it is ok to test pH with chlorine levels up to 10ppm.) Anytime your chlorine is higher than 5 or 10, depending on the kit you are using, you can dilute your sample before testing pH. Take 1/4 cup of pool water and mix it with 1/4 cup of distilled water. Then, run the pH test as normal.