I think the purple fanwort ID above is incorrect. It looks like either parrots feather or Eurasian watermilfoil (both belong to the same genus).
Not certain about the mystery-plant. Looks a lot like partially dessicated or deformed coontail; but your white-flower comment threw a wrench into that theory. Coontail flowers are very small and fairly inconspicuous. Actually, it looks like coontail that is reacting to the effects of 2,4-D. Is that a possibility?
I can't contest the widgeon grass photo, but neither can I confirm it. Looks like something my dog upchucked
