My mimulus are flowering then seem to shut down and die off, bizzie Lizzie and begonias around them are all fine. What do I do to encourage more flowers!.
Just off the top of my head, I would keep the mims well watered, as they like wet conditions.
Secondly, you could try dead-heading the flowers to encourags a 2nd flush.
I've seen mimulus growing wild. They were in a flood plain and even when dry weather the ground was soft. I think that they will need a lot more water. Hope this helps.