Yeah that seems to be the situation as you described there. Noticed the curly leaf pondweed back in June forming a ring around the deep edge of the lake. Once that died off, initial weed growth was only moderate until the herbicide treatments which seemed to kill most of the deeper weeds remaining around the lake. Better weed growth was in the extreme north and south ends in shallow water but a lot of that stuff didn't seem the healthiest either.
Seems the herbicide treatments might be doing more harm there than good.