I was looking at my hygro plant yesterday and it appeared that the bottom of the stem had turned brown and I could see little white threads coming off it, like it was rotting. I took the plant out and sure enough the whole bottom basically broke off. I stripped off all the brown stuff on the stem. It had already sprouted a couple of roots from the side, I guess it did this when the lower roots started rotting. So I planted those roots into the gravel as best I could and I stuck the bottom of the stem back into the gravel. I hope it lives! Today one of the newly sprouted leaves has a funny look in one spot but other than that it's still living. What would cause rot to set in?