I guess 90% health at a year is normal if you charge overnight.
My 2.5-year old iPhone X is at 93%, and my 12 mini purchased in February is still at 100% health. I charge for about 30 minutes in the morning if the phone is low, but otherwise I normally only charge in the car with an occasional 10-100% charge cycle to re-calibrate the gauge.
Unless I find a fix for the idle drain on my 12 mini, I dread the runtime with 10% or more degradation.