I had renters that did not pay thier last few months of rent before we evicted. Can I write those months off as a loss ?

Sorry no.  You cannot have an expense for loss of rent for rent never received.

No, you cannot deduct the loss of rent. If you hold a property for rental purposes, you may be able to deduct your ordinary and necessary expenses (including depreciation) for managing, conserving, or maintaining the property while the property is vacant. However, you can’t deduct any loss of rental income for the period the property is vacant.

Please view page 4, IRS Publication 527 for more information about this rule.

https://www.irs.gov/pub/irs-pdf/p527.pdf