Pins 9,10,11 should be working off TIMER 1 which all use the same pre-scaler, so I dont know how 9 and 10 can have one frequency, and 11 have a different frequency.
Unless D11 is configured as OC0A instead of OC1C, which means that it will work off timer 0.
TCCR0A &= ~(_BV(COM0A1) | _BV(COM0A0));
TCCR3ATCCR1A |= _BV(COM1C1) | _BV(COM1C0);
...
OCR1C = ...;