Inherited Smokers - Security Deposit Question

[Matt McGuire]

I recently bought a 4-plex with 2 units occupied and 2 vacant. I painted both of the vacant units because there were smokers before and the walls were yellow. The other 2 tenants have indicated they will be leaving when their lease is up and they both smoke. Their security deposit is only $400 which doesn't even cover the cost to paint the whole unit. 

I'm sure it will come up, so what do you guys think? Does smoking in the unit constitute wear and tear or should I keep the deposits to paint?