If you submitted a contract, ask your attorney or agent to prepare amendments on the price and be prepared to wait .
If your offer was just that, an "offer" and not binding, sure, renegotiate the place has likely lost value since then anyway. If you have signed a contract speak with your attorney. Hopefully there was a appraisal clause protecting you from paying too much.
I suspect if you make a change - which I think you can unless you are already under contract - that you will enter into another protracted approval process. And as you have already experienced, short sales are anything but short.
Good luck and best,
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