This is discriminating based on family composition.Other ways of looking a this might be impressions from Facebook search, has bank account, willing to provide vehicle registration/insurance info, smokers or not, application filled out perfectly, impressions of being overly fussy, demanding, or dramatic.  

They have been paying on time since I bought the property and have been good tenants; however, they both have cats and dogs, are smokers (outside), and the amount they are paying is ~$200 below market for unit A and ~$100 below market for unit B.

Wondering how about the smelling issue from a smoker next door?

It would be like trying to get car insurance on a totalled car, or trying to get health insurance as a smoker AFTER you've been diagnosed with lung cancer (in a world without ACA). 

She was a very heavy smoker and I wanted the building smoke-free, so I got her to move anyway. 

Although I don't think "weed smoker" is a protected group.

The majority of the tenants I've taken over are elderly, smokers, had pets, some form of government assistance, etc. and the really bad ones are super nice from the little time I’ve talked to them as “new management”.

Previous owners smokers, ceiling looks rotted and insulation is coming through 3 large spots but she says it’s been repaired.

Assuming the pot smokers are not your tenants and this condo is owned by someone else maybe reach out to the landlord or HOA?

This is similar to saying "No smokers" or "No pet owners" as neither of those are considered to be protected classes.