answer:I’m not sure. If it is because of over-watering due to excessive rain, which seems logical as many plants will experience root rot under this condition, you would want to dry the soil out by not watering for a while, keeping rain out, and hopefully setting the pot under some serious sunlight. Alternatively, you could basically replant it in new soil. If you get a lot of rain, or if you have a very clayey soil, you might want to consider mixing the soil with some kind of rock or other aggregate or even potting soil to get better drainage. This site says excessive water will lead to root rot.