Why are My Chrysanthemums Turning Brown?

Are you talking about the flowers turning brown? The flowers on my mums are turning brown and I am hoping someone has some feedback on this. My mums are planted in the ground and get plenty of water and sunlight.

Yes, they need water and sunlight. Pinching back is done in the spring and early summer, to shape the plant and get it to form more branches and thus more flowers. The pinching should be stopped by mid-July.
Mums will not survive in a container outdoor through the winter. In fact, many mums sold now don't survive in northern climates planted in the ground. The growers are choosing less hardy varieties and we get to purchase them every year. If you do plant them in the ground, do it asap and be sure to mulch the plants heavily after the ground freezes. This will protect them and keep them from heaving out of the soil in freeze/thaw cycles, which exposes the roots and kills them. If they pull through the first winter, they should be better established next year and not need as much protection.