Building Houses Evenly in Monopoly
You played within the rules. Houses must be built up (and sold off) evenly within a color group, but different color groups can be built up differently without regard to each other.

The section of the rules you quote is exactly the section that supports your play. 

Addendum: not an official source, but this same question came up on boardgamegeek (with the same answer).

https://boardgamegeek.com/thread/435348/confuse-about-building-evenly