2000 Accord 2.4L MT coupe with about 195k on it. Got the car used 2 years ago.

I feel vibration in the CAR and PETAL when I ACCELERATE between 45-60mph. I only feel it when I accelerate and goes away when I don't give it gas in between those speed. I do NOT feel it in the steering wheel so that would rule out the possibility that I need a alignment or wheel not balanced. Also I got new tires and got an alignment and still have this vibration.
If I rev the engine parked and on neutral, I don't feel any vibration no matter what RPM I am at. The engine feels smooth.

The 2 side motor mount looks like it was replaced but not sure if the rear got replaced or not. Does this symptoms of a bad motor mount?

If I am going to replace the rear motor mount, does it make sense to replace all of them as well? Motor mount is about $20 each and that isn't much if it gives me a peace of mind.

Also does anyone have any links to How to on replacing the rear motor mount? I only saw on youtube video and it is for an automatic transmission. From what I read up, manual transmission is a little different.

Any help would be great.
Thank