Thanks so much for your concern. The fruit tree spray is just the spectricide once and done that you buy at lowe's and I mix it according to manufacturers suggestion. I have used it before but must admit to having used it a little more this year due to increase in Japanese beetle pressure on fruit trees this year. But I've not used more than is recommended on label.
I really can't think of anything I've done this year that I haven't done in the past, but my pond is lower than its ever been and water very well could be stagnant and/or problematic, so I'd say that is a good guess. I have another chicken that I'm quite sure is dying so I will have it necropsied asap if it does!
Again, thanks for all your concerns and efforts to help.