Could hot water heaters be causing bothersome vibration?

Since I first reported my vibration problem here, I have learned that the management company has installed two hot water heaters on the roof in the area of my condo.

I am on the 3rd floor, the top floor. Could these be what is causing the vibration?

When it was warm weather, I felt it more often, and I think that could be a fan. Now that the weather is cooler, I don't feel it as much during the day, but when it starts late day and evening.

I thought maybe that is because people are showering more.

Has anyone had a vibration problem due to hot water tanks? Thanks.