Offer contingency broken

[Frank Jennings]

I recently put a 9-unit apartment building under contract. It was 100% occupied. Two of the 9 units had a lease, but the other 7 didn't and were month to month. I put a contigency in the offer that all the apartments needed to have leases and also 100% occupancy. Today was the deadline and 1 tenant declined to sign the lease and will now vacate the apartment. The rent was $450/month.

I don't know what to do. Should I ask for a concession in the form of cash at closing?