Dude Waira nailed it on the head. I have had this problem couple times on plants in small containers that needed watering more often just try to scrape a good amount of the infected area of your medium out and replace it if u can the more u remove around the infected area the better. I only used some antifungal Shit my brother gave scraped the whole surface of my medium about an inch maybe more deep I'm some spots and replaced it with new pro-mix hp kept the rh under control it didn't spread to any of my branches or leafs though. Just a suggestion it worked for me so that's my 2cents. ✌brother
