Q.Why My Young Chrysanthemums Whither?
In additional to play with wet-dry soil can I use something else to help my chrysanthemum? Can I use Neem Oil on foliage?, or Trichoderma for soil?

Certified GKH Gardening Expert
Unfortunately, your photos did not come through. I am unable to see the issue. The correct actions to take will depend on what is causing the wilting. If this is fungal, or bacterial, in nature then fungicides will be the option. If this is from over, or underwatering, then correcting watering habits will be necessary.
Since most of the Trichoderma species found in soil are, also, found in ambient air, chances are that it is already present in the soil. Adding any more will only be beneficial to an otherwise healthy plant.
In the meantime, here are some articles that will help:
https://www.gardeningknowhow.com/garden-how-to/info/using-fungicides-in-garden.htm
https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/testing-moisture-in-plants.htm
https://www.gardeningknowhow.com/ornamental/flowers/chrysanthemum/growing-chrysanthemum-flowers.htm