2014 Chevrolet Cruze heater

2014 Cruze, heater quite blowing hot air unless turned up to 80. I used to set it at 75 until cabin was warm, then down to 72 to maintain comfort
Live in So Calif, cold day here is in the 40’s, slow to warm up. I suspect thermostat but no CEL. No leaks, reservoir at proper level.

I’d suspect the t-stat, too.