Over collection of rent doesn't eliminate the notice to vacate, they're still legally obligated to vacate on the 15th.

I used a HELOC for my half of a down payment for a vacation rental property.

Given that it's almost a 50% increase from the existing rent price, you might want to set a timeline of 2 or 3 months before it taking effect so they can find alternative housing if they plan on vacating instead of staying at that price point.Another option could be to ask for the rent increase, but offer something in return.

We are a vacation property so people who plan tend to book ahead of the Airbnb crowd.

(Max vacated rents - your monthly mortgage payment) = +/- net cashflow.

I understand that my lease is set to expire on July 15th, and I was asked to vacate by that date.

For the bulk of my real estate service career I've sold Oregon Coast property and STR vacation rentals with ocean views and occasionally oceanfront locations. 

Couple of observations here from my perspective:-I would have gotten the "old tenants" to sign a vacate agreement wherein the agree that they are not entitled to pro-rated rent for remainder of that last month. 

You can track materials used to fill in your JIT processes or whatever.With a vacation rental, it is always different.

Think of anything your tenants need to do before they vacate the property!