I've had lily of the valley over the years in different locations, but I've never seen this.

Last year my neighbor & I transplanted several under a tree with an annoyingly extensive root structure -- it was quite difficult to find space between the roots to transplant them (another neighbor had sucessfully used them to cover up the protruding roots under her tree). They did not appear to do well, yet this year they've spread and are doing well.

While fertilizer can't hurt, I'm pretty sure it's not the tree roots.

I have LOV coming up through the spaces in my flagstone path. They spread out in all directions once established. The ones trying to come up in the spaces are crumpled and stunted. They don't like being walked on, but I didn't plant them there......
I've had some hostas look that way after work men tromped all over them as they were emerging.
Perhaps someone walked on your Lilies of the Valley when you weren't around? Perhaps a neighbor's cat or dog decided it was a convenient place to pee?