Reimbursing Tenants a Portion of deposit (Repair bill was more)

[Kerry Arm]

Thanks in advance for all who take the time  responding to my question. I purchased a property with student tenants. I agreed with the seller that the current tenant could remain in the home since they only had a few months remaining on their lease and it was rental income to me. A couple weeks before the tenants moved out, they reached  and stated all the damages in the apartment was not their fault. 

I understood they had a roommate several months before the sale was made but within the lease year.

I had the unit repaired and decided that charging them 60% of the repair bill is fair.

Does anyone think this is a reasonable solution or has anyone experience a similar situation? If so how did you handle it?

Thanks Again