Monarda leaves problem

[BearsPaw]

Hi everyone! My monarda has some brown/black spots on leaves, they dry out and eventually fall off. The plant gets quite a lot of light and air circulation. I thought it could be powdery mildew as it seems to be a common problem with this aprticular plant, but for me it doesn't look like it.
Any suggestion welcome!

 

[oneeye]

The soil is staying too wet in the root zone. Aerate around the base of the plant gently with a hand cultivator to allow the roots to get air down a little deeper,

 

[BearsPaw]

OK, thank you, I'll try to do that!