Yes, you can unlink a Performance from a Price Profile and set specific capacities for that Performance:
Select the Performances tab on your event
Click Manage on the performance you want to unlink
Scroll down and click Edit Capacity
Set the capacity for your Bands on this performance by clicking the pencil icon next to the band and entering the new capacity
This will then unlink it from the original Price Profile, and create a new specific Price Profile for that performance only
NOTE - this means that any changes on the original Price Profile won't pull through this performance.