Sting- Flourite doesn't have fertilizer in it persay to rinse away. The whole of it is flourite clay and you won't harm it by rinsing. What you rinse away is the same as what is left except smaller particles.
I'd probably do another couple of water changes, even though it sounds like a PITA.
If I may ask, how much flourite did you buy and how deep is your substrate? I'm thinking of getting a 55 and want it fully planted, too. How much was it per bag?
I just went and checked the 15 lb bag I have waiting for the next tank and it says that it will cover 217 sq. in. to a depth of 2 inches. I'd guess you'd want at least 3 or 4 bags for a 55, depending on how deep you want the substrate.
Someone, I think at Aquabotanic's forum, mentioned using a pad of newspaper instead of a bowl to cushion the waterflow. As the water level rose, the newspaper rose with it.
WetMan, who I generally trust, has mentioned that rinsing flourite reduces its effectiveness. When mine goes in I'll probably rinse it anyway to avoid the clouds. I clouded up my last tank by remodeling the laterite substrate at the last minute. The sediment clogged my filter and settled on the heater, creating a hotspot and causing it to shatter (just another wrinkle you may want to be aware of).