I tested at noon at it was at 7.5, I have roughly a 55 level CYA so i shoot for 7 - 9 so I added 7 cups to raise it to 11. I checked it at 9:30pm expecting it to be around 7 or 8 and find it at 5. Is this a normal loss? My water is 90F and it was really hot today and the sun is on the pool unfettered for about 9 hours each day. My overnight tests have been fine (did one a few days ago) and the water is crystal clear so just wondering if that is normal. I still haven't found a routine where I can add enough at night and not have to worry about it until the next night. Any help is appreciated.