Some good points here, but I also think there is more that can be done. I'm going through a very similar situation right now with one of my tenants and this forum has helped immensely. I think we are both nice guys. As one of the YouTube real-estate personalities I follow has said: "Nice guys finish broke." -- Ernie Garcia. My generalizations below are from my experience so take it for what its worth and here is my experience.
The family moved in. Three months later I do an inspection and maintenance visit. Boxes and piles of everything everywhere. Most of it appeared to be worthless stuff. The garage is completely full and there is some junk in the back yard. It was a safety and health hazard. A rescue crew in the dark would never be able to navigate it. With so much stuff everywhere, I knew pests would eventually come. I've never had a tenant near this bad before. I verbally told them they need to clean it up and they provided excuses. I then come back 2 -3 months later for another maintenance visit. Everything is the same. I provided them a written notice and sent it certified mail. This was a demand letter, but didn't follow the state requirements. I come back 2 months later and nothing has changed, but we now have mice droppings across the house. Now I write them the official 10 day notice per AZ law. As the end of the lease is a few months away, I also write a notice of intent to not renew the lease. I verbally tell them that if they can clean things up, I'll reconsider, but by now I'm 90% sure they won't put in the effort. One more inspection 30 days later and nothing is cleaned up. We are now about 2 months away from the end of the lease. In summary nothing including threat of loosing this home spurred them to even try to clean up their mess. Now the mess includes fast food boxes and papers everywhere. fries on the floor and vermin. Spilled and splashed drinks everywhere. So far they have paid rent in full and on time, but per a conversation with the last landlord after they moved in, they skipped out on paying the last of the rent to him and never returned the keys and left his place a mess. I'm prepared with this knowledge now.
In AZ, a tenant can pay any amount of rent. Even $50, and if the landlord accepts it, he cannot evict until he starts over the next month. As such and in preparation, I stopped using Zelle and have now switched to an online site for rent collection that only accepts payment in full. If they don't pay the last month for me, I will immediately start the process with a 5 day notice and then an attorney taking over.
If I were to do this over again knowing what I now know, I would have immediately served them the 10 day notice after my 1st inspection and then 10 days later another notice as they likely wouldn't have complied. Photograph everything. After two notices, I would have started the eviction process. I've lost a lot of sleep and had a lot of stress from this family. In addition, the home has physically suffered. I vow to never let a tenant control me like this again.
I never allow vaping or smoking of anything anywhere on the property so the cigarette butts would also be an immediate eviction. I hate the smell of cigarette smoke and definitely don't want it in my property. Cleaning up after a tenant who smokes is expensive also.
At 5 months away from the end of the lease, I'd now suggest you follow your state's guidelines for sending a fix or quit notice and doing it immediately. At minimum out of respect for the downstairs tenant. I always treat my tenants respectfully and don't appreciate tenants who do otherwise to me or neighbors.
You don't need any excuse to go in and look either. Simply provide notice. 48 hours is required here, but I generally provide greater than a week notice. I go in, change the air filters, replace smoke alarm batteries occasionally, I check for leaks under every sink. In doing so I get a good sense of how the tenant is treating the property. I take pictures of concerning things I observe and file it away.
You need to need to stop being a nice guy. Do your inspection. Send the 10 day notice to fix or quit or your local equivalent. If your place is like mine, its only going to get worse over the next 5 months. Get them out.