RE: New to electric park flyers
Most motor mfg will provide recommendations as to what prop to use on their motor. You match the prop to the motor not the plane. Go back and see what the mfg recommends.
While the ESC and the battery might not be hot, how was the motor. You could be working within the range of the batery adn the ESC and be over stressing the motor.
Just guessing, but I would think you are still too big in that prop. Something 9 inches or less might still be in order. You could still be over working the battery pack or the motor.
Do you have a watt meter? Or do you have an amp meter that can measure 20 amps? If so, I would try to take a measurement remembering that you static measurements will be higher than what you will see in the air. Where glow planes are tuned by pitch and RPM, electric systems use the watt meter in place of the sound of the motor.