I'm sure you'll be fine, I live on the 6th floor in my building and I've had a 75 gallon & 55 gallon in the same room without any issues. And, now I have a 100 gallon and a 55 gallon going where I had the other tanks, and I haven't had any issues at all.
But my building was built in the 1960's, and was originally made with concrete floors between each floor of the building. But I know a guy with a 135 gallon in his 5th floor apartment on the east coast, and he doesn't have any problems.
15g Fluval Flex - Will be a planted shrimp tank