Did you planted your marsh marigold in partial sun to full shade?
Did you planted your marsh marigold in a consistently wet, slow-draining soil?
Do you allow the soil to dry between waterings?
Do you feed your marsh marigold regularly?
Do you prune your marsh marigold regularly?
Do you keep your marsh marigold free of pests and diseases?
Marsh marigolds will bloom consistently in part sun to full shade. South-facing or west-facing direction for best results is the best for these plants. Where summers are very hot, or in areas of direct sunlight, the Marsh Marigold may go dormant after blooming. Expect the foliage to wilt and die, and look forward to the following spring’s show.
Marsh marigolds love rich, moist, or boggy soil that is damp to fully submerged in water. If planting in a rain garden, situate it near the center of the lowest spot. They can also be planted alongside other bodies of water such as streams, and they are often the first pond plants to bloom in early spring.
Don't allow the soil to dry before watering. Keep the soil very moist at all times. If you haven't planted your marsh marigolds in a boggy area like the woodlands, a rain garden, or near a body of water you will have to irrigate it constantly.
Fertilizing is not usually necessary. This plant can get all nutrients it needs from the boggy soil.
No regular pruning or maintenance is needed. You can only trim off dead leaves and flowers to keep a more tidy look.
Good job! You are taking good care of your marsh marigold.
This water-loving plant is not subject to significant attacks by insects. In some circumstances, it may have problems with rust and powdery mildew. Any affected leaves should be cut off and removed. The appropriate fungicidal spray will protect your plant from further infections.
https://www.thespruce.com/growing-marsh-marigold-5079019
https://plantcaretoday.com/marsh-marigold.html
https://www.gardeningknowhow.com/ornamental/flowers/marsh-marigold/growing-marsh-marigold-plants.htm

Sreten null
Hi! I’m Sreten Filipović. I graduated from the Faculty of Agriculture at the University of Belgrade, with a master's degree in Environmental Protection in Agricultural Systems. I’ve worked as a researcher at Finland's Natural Resources Institute (LUKE) on a project aimed at adapting south-western Finland to drought episodes. I founded a consulting agency in the field of environment and agriculture to help farmers who want to implement the principles of sustainability on their farms. I’m also a founding member of the nonprofit organization Ecogenesis from Belgrade whose main goal is non-formal education on the environment and ecology. In my spare time, I like to write blog posts about sustainability, the environment, animal farming, horticulture, and plant protection. I’ve also published several science-fiction short stories.
You can find me on LinkedIn at https://www.linkedin.com/in/sreten-filipovi%C4%87-515aa5158/