Help with troubleshooting heater
 

2012 CX-9. Heater is noticeably less hot when I'm idling versus driving. I have the temp set to 90, but it's pushing out 75 degrees at idle. When I'm driving, it will heat up to almost as hot as it used to be (before these symptoms). Also, the passenger side seems to be a couple degrees hotter than the driver side when they are set to the same temperature. Back zone seems diminished also, but working better than both front zones. Everything A/C works in all zones, and the amount/force of the air is as expected. Just the temperature is off.

By the way, I estimate 75 by starting at 60 and feeling the temp as I notch it up one degree at a time. At about 75/76, I'm not able to feel it get any hotter.