Desert Marigolds are having problems
The flowers have been turning black. And the other issue is the leaves have started turning kind of yellowish with spots. We can't seem to find anything that matches our problems. We hope you can help. Thank You
Marigolds are generally resistant to pests and issues, but this sounds like a fungus problem.
Remove the black and diseased parts of the plant and dispose of and treat the plants with Neem OIl. I would use weekly until the plants improve.