​Overheard managers talking smack

So, I own a small business. I started it out of my home, as one often does, in 2015. It’s grown over the years, thankfully, and I have a storefront and employees to work in it while I produce the products.

We’re opening a new location and need to hire some folks. I have 2 women who I have appointed as the managers of the shop and they were to interview people, etc. I asked what time so that I could meet the people coming in

They didn’t tell me. I looked at our cameras to see if the interview had started and overheard some shit.

First, I overheard them bitching to the prospective employee about how I hired a young person that they didn’t like and how I didn’t consult with them beforehand. 🤔

The person left shortly after and they immediately launched into some rant about me.

I haven’t even seen one of them for weeks, as she was off on her second vacation of the summer.

My question is: do I ask them about why they’re so upset and what the heck I could have possibly done to make them mad? I overheard it on the camera – do I mention that or just ask them generally?

To add: I’m a female, mid 40’s, as are they.

The issue is, they both are/were my friends when I hired them and I thought everything was great. We have meetings where we go over stuff, they’re supposed to help manage the store so I can make the product.

I pay them well, just gave them both a raise, they take whatever time off they want, they make their own schedules…

So how am I the bad guy? I want to confront them and just don’t know if I should.

Any suggestions? I