You are probably losing FC to the sun mostly. The CYA will help slow down chlorine loss. Give the socks a squeeze from time to time to help it dissolve quicker. 30 is a good start. Don't forget trichlor pucks also add CYA.
I would say that everything, including the pH, is looking normal. And it is difficult to get identical test results at your levels. So don't about those minor changes in your tests.
I would like to know if you are seeing any white plaster dust come off the surface when you brush the walls and floor?
And you did wait six hours before starting the water?