I'm going to throw something out here since it appears to be the root of this problem.
I'm guilty of fertilizing my lawn. Go ahead and shoot me. I like green grass and the healthier it is the less weeds I have to kill. I tried several brands and kinds of fertilizer with a wide range of effects. One , 15/15/20 mix from the grainery caused nearly flourescent green streaks in the water almost imediately after a rain. Other types simply made my grass grow like crazy.
Currently I'm using something that starts with an Sc and ends with ott's. It's their cheaper line and has 2% iron too. It's 29-3-4 and slow release. I have had no problems and almost no weeds in the pond even though I fertilize right up to the edge (a slightly lower rate around the pond). It keeps the grass nice and green and doesn't seem to need to be mowed more then unfertilized lawns.
Maybe you're neighbors need some encouragement to simply change brands or suppliers. I'm curious if most of your neighbors are receiving their treatments by spray from the back of a truck. I haven't been too impressed by the spray truck guys I've encountered or their products and "professional" granular application is often a competitively priced alternative.
