I transplanted one of my lilies late this year--June I think. It has leaves finally but not blooming. We've had a crazy summer rain, hot then cold and cold nights but I think it was transplanted late. I don't know what matting is but if you've used it before is probably just that have transplanted late. They should be fine next year.

The first thing that comes to mind is has anything changed? Are the lilies getting less sun due to tree growth or other factors? Are the Koi getting enough food so that they are not devouring the lily roots?

If everything is relatively similiar to previous years then the lilies are most likely just set back after the dividing and should be really nice next year.

it doesn't sound like enough fertilizer. Most of the water lily tabs say to fertilize once a month.