Dying E. hookeri
In order to diagnose the problem, we need a little more information.
-Is it inside or outside?
-What kind of light exposure is it getting?
-Have you added any fertilizer?
-Has anything changed environmentally (repotted, different watering schedule, moved, different light exposure)?
The plant is inside. It is getting light about 8 feet from a bay window. It was outside from May-September where it got a TON of rain but grew and bloomed beautifully. The blackening started about one month after moving it indoors when new fall growth began to appear. I have given it a weak Miracle Gro treatment in water once every few months. It has been watered significantly less since being brought in. Maybe once every 2-3 weeks because I was concerned about how much it was rained on.
It sounds like the issues are environmental. It is going through a state of acclimatization as it gets used to the new indoor environment. "The gardener should acclimatize plants when placing them outdoors in summer by gradually increasing light intensities, and reverse the process again before plants are brought indoors in the fall." (Indoor Plant Culture https://pubs.ext.vt.edu/426/426-100/426-100.html#L3). For plants grown in high-light conditions, acclimatize them by initially locating them in a high-light (southern exposure) area of your home and gradually moving them to their permanent, darker location over a period of 4 to 8 weeks.
Because it got so much rain outdoors and is only being watered every 2-3 weeks, the browning could also be due to lack of water. You might want to try a more gradual decrease in water (1x per week for several weeks then 1x every two weeks for several weeks...).