LeeAnne, if there are Canadian geese in the lake, it is also possible that excess goose poop is what is burning these lotus to death.
We have a horrendous time with Canadian Geese on our Sod Fields at work. The poop is the size of large dog turd and
very toxic/acidic.
Burns holes all over the sod. Problem is, not easy to clean up because they are not firm. (they look firm but don't let that fool you!)
Very loose. Blech! And if you try to wash them away, it just burns a bigger hole in the sod.
We have employed all sorts if gadgets on the sod fields, but in the end, what works best is these rattling metallic shiney flags.
They are these size of a black lawn bag flattened out. On a metal stake so the bag just touches the ground when limp.
Makes a racket in the wind, and the movement scares the geese. Have to be placed about every 50-100 feet allover the sod fields.
Expensive too not to mention manpower to put them up and take them down when mowing or harvesting. And in the fall-winter, a lot of them get blown away or shredded beyond any use.
Anyway, Canadian Goose poop is horribly toxic. Way worse that ducks, etc, mostly because of the sheer size, and volume Canadian Geese can produce!
But most of the local golf courses have employed 'Goose Dogs', which are dogs trained to chase geese off the fairways and putting greens.