Vibration/rumble at highway speeds?

Update,
The vibration came back again under the same circumstances as described before, stopped and checked all wheels and brake rotors for excessive heat all seemed normal, brakes feel normal when braking as well. That being said, I was able to wedge my phone up into both driver and passenger side wheel wells to take photos of the CV boots connecting to the transmission and found that both have some grease/fluid on or around them. I am not sure if they look 'bad' enough to cause the issue I'm having, I'm certain they don't look normal though. My next question would be, would failing CV joints/axles create a vibration at a specific speed that goes away completely when letting off the gas or would the vibration be dependent on the speed the wheels are rotating (a constant vibration that occurs between X and X mph on or off the gas) I worry there may be an additional underlying cause to the issue I'm having. Thank you.