Noob landlord in need of help with next steps

[Chris Themelis]

I'm a very new landlord dealing with my first tenants, in my first ever rental property (Washington State, Snohomish County), and really need some advice/guidance.

Background: I have a large 3-bdrm condo that is being rented to 4 tenants. The tenants are on separate leases, but responsible for the shared total monthly rent. Each month the tenants pay me their individual portion of the shared total. The lease is through July 2020.

In December 2019, 1/4 tenants did not pay rent (lets call him Mike). Turns out, Mike also decided to move out without notice, due to one of the roommates being a horrible person. I told him that he's still responsible for paying rent, and notified him of his late fees. He asked if he could find a replacement/sub-let which I agreed was fine, pending my approval. Mike has yet to find/send me a single option for consideration.

Fast forward to now. Mike has yet to pay me for Dec, and is now late for January. He says he has 5+ candidates lined up for me to consider this week, and is planning to pay me for Dec by end of week.

The other 3 tenants have paid me for January 2020, but a second tenant (lets call him Jeff) stepped forward to ask if he can break the lease and move out because of this same really bad roommate. I told Jeff that I would follow-up with options after looking into it.

My plan/questions/guidance needed: At this point, I'm wondering what to do (I realize that I should have just served them a 14-day pay or vacate in December, but I'm still learning). My tentative plan is to serve them a 14-day pay or vacate, then offer the option to break the lease early if they can come up with 2-months rent (for Feb/March). I'm not opposed to replacing Mike and Jeff with sub-letters if they can find me replacements that I approve of. 

I have very little sympathy since they chose to enter into an agreement and live with a ****** roommate, which is completely their fault, but I want to be a reasonable human. 

Does my plan seem appropriate or should I take a different approach? Are there any options I'm missing?

Thanks,

-Chris

TLDR: 3/4 tenants paid me for December and January; 1 of them has not. This same tenant also moved out without giving notice. Another tenant has stepped forward and wants to end his contract early due to roommate drama. Should I serve a 14 day pay or vacate then provide the option to break the lease and/or allow them to find sub-letters that I approve of? Are there other options that I'm missing?