Hot water issue in my showers

I recently purchased a newly renovated home with all new plumbing and Moen fixtures. I’ve noticed in both of my showers (one on the second floor, one on the third) that the water will go from hot to luke-warm shortly after turning it on. I have the hot water heater cranked (new, gas, 80 gallons) and get piping hot water in my sinks. Wondering if anyone has a good resource for adjusting the water mix in the showers. Thanks!