vmckague, I'm not a Lotus expert, but have noticed that after they bloom, they're done for the season. No more blooms, and too much fertilizer may burn (or kill) them.
Hardy water lilies are different. As long as they have fertile soil and good sun, they will continue to put out blooms. Maybe not as many as the first flush, but the good bloomers keep on blooming. Sometimes they go well into October (zone 5 here). Keep the dead pads & blooms trimmed off for the best display.
In August, the sun changes it's angle and if you have tall trees to the south, they start shading the pond, and blooms decrease.