Hotend won't hold temperature with PETG

I recently switched to PETG and coincidentally or not, the hot end has begun having difficulty maintaining temp. It’s 20* below requested temp right now. 245C vs 222C actual. I’ve done the PID autotune and the new values didn’t make much of a difference. Do I start with the cartridge heater or the thermister?

Thermistor is more likely.

Well, I switched back to a .35 nozzle, bumped the bang_max and PID_max to 255 and that seems to have helped so far.