Beginner Gardening: Dianthus are dying, fungus or heat? Please help!, 1 by BarbS2187

BarbS2187 wrote:
This is my 1st garden in our new home. I was so proud of all my hard work. Everything was thriving! I deadheaded my flowers 2 times a week and they had so many blooms that they were just beautiful!
The heat came, then my Dianthus stopped producing. Someone told me to trim the tops of the stems and they would produce more. I did this and now 2 weeks later, they are all turning yellow and dying.

I've tried....
Loosing the soil to get more air, watering more, taking off the dying leaves,

Not sure if my trimming did this..the heat is doing this..or is this a fungus? Please help!

I'm including a picture so you can see what they are doing :o(