How to approach Lease Violations--Rookie First Timer Landlord

[Timothy Burns]

To clarify my situation, I am in my first year of landlording, househacking a duplex, so I live next door to tenant. 

Tenant hasn't even been here a full six months and has broken the lease I feel several ways, but Im not sure how to approach. 

1. Smoking excessively: during pre screen tenant stated that they only smoke outside, but now the bedroom smells like an ashtray and they are leaving butts all over the premises. 

2. Pets: stated clearly during pre screen that they would not have any pets becuase they didn't want the extra responsibility, but they now have a rabbit. 

I first became aware when I was working on the kitchen sink and saw a bag of rabbit food under the sink, and since then have confirmed that they do indeed have one, but they are not aware that I have seen it. 

3. Longterm guests: this one doesn't bother me as much but they have a minor that has basically been living there, not so much that I don't like them staying, but I believe she's been doing laundry over there (can't really prove that)  and I pay for water/sewer. 

I have been taking pictures of all this. 

Not sure if I should just go ahead and put a notice to comply in the mailbox or are there other steps I need to take first?