Pools will typically lose some water over time due to evaporation, splashing and backwashing. Due to a difference in temperature between the water and air, evaporation may be more prevelant on heated pools mixed with cool nights.
If you feel your pool is losing more water than normal, it’s best to perform a bucket test.
Place a 5 gallon bucket on the top step of your pool and fill it up to the same level as the water inside the pool. Refrain from swimming and backwashing until your test is complete. Observe the bucket over the next 2 days to make sure both levels remain the same. Should the water in the pool drop lower than the water in the bucket, the pool is leaking.