Welcome to TFP! Good to have you here
It's possible that you could have a lot of dust in the air and the pool would benefit from vacuuming that often, and many people do use cleaners in larger pools that run every day. It could also be a bit of algae growing and then dieing in the pool, and sinking to the bottom. It can be challenging with a water volume of 1200 gals to keep the pool sanitary and kill all algae. I'll post two links, one that's about running a pool your size, and another about how Trouble Free Pool Care (TFPC) works. The method in the first link is designed to be as easy as possible when it's also reasonable to drain and refill the pool occasionally.
Pool School - Guide for Seasonal/Temporary Pools
TFPC for Beginners
Come on back with questions or feedback. Cheers!