I am running my XFX cards, including the the Black Edition, at 1191 gpu core and 2191 vram. Most of them are consuming, per GPU-Z, between 72w to 80w. They are pretty awesome cards. If I had to guess, the card may be starving for power... The other situation I have encountered where all my cards running at a lower frequency was due to software settings that needed to be cleared.

Try following these steps to see if you could figure out why the card isn't getting over 2100.

1. Restore GPU to stock rom.
2. Run DDU (assuming windows) in safe mode to clean out drivers.
3. Reinstall Crimson drivers 16.11.5. Reboot. This does not make sense but it would undo settings that are set by software such as MSI Afterburner, before you mine, go to Radeon settings and reset the configuration to default for all cards.
4. Mine and you should see 24MH/s.
5. Mod the orignal rom and change the timings only, then flash to card. (assuming rom name v1)
6. Mine and you should see 28MH/s.
7. Mod "v1" and up vram frequency to 2200. (saving rom as v2)
8. Mine and you should see 29-30MH/s or more. Ensure that the hash rate does not continue to drop while mining. Monitor with GPU-Z and watch the GPU and Memory usage %. It should stay at 100% if the card likes the mod.
9. Repeat steps 7 and 8 until you see that stability.
10. Once you get a stable vram frequency, proceed to tune the core frequency if you would like to be more power efficient. Otherwise, all done...

I have not encountered a card that can't go above 2100 yet but that could be a crap shoot really... some may say to look at the ASIC quality in GPU-Z but I have a card that is 64% that outperforms another card that is 92%. Go figure!

Hope this helps!