my bee balm plants have the very same problem, little white worms in each bloom. I shook sevin powder all over them and it seems to have helped, but the plants are spindly and blooms only come out about a quarter as normal.

Hi, The use of Sevin can help in controlling the insects in the flowers. As far as plant conditon can't really say for sure why they may not look as good as they should without actually being on site to evaluate. However, if teh plants are growing in a drier area of the garden they tend to be a bit more thin and open than if well supplied with moisture. If the plants are old and may need division that can also affect plant quality.