I think you are doing good, low here was 48 last night, again we get bigger temperature swings being 100 miles inland. I went swimming just a bit ago, and the water temperature was 81 degrees with the solar running during the day all week, with clear skies for the last week or so. Lows have been in the upper 40's to mid 50's most days, and highs around 80. Of course my pool is indoors which changes the dynamics a bit, on the one hand you don't get the direct sunlight warming, but on the other you do get some added insulation and a bit of a green house effect during the day. I like my pool water about 83 -84 degrees, so I think the solar cover will be going on next weekend which should help keep it in swim temperature range for a few more weeks with a bit of luck. (we have a slight warming trend with mostly clear skies expected for the next 8 or 9 days, otherwise the solar cover would have went on today).
Ike