Very strange. Those symptoms coming on so suddenly point to some sudden stress such as being left in a hot car, roots drying out, or ????.
I suggest you discuss the plant problem with the retailer where you purchased it. In the meantime keep the roots moist but not soggy. In time if the initial damage was not too severe it should recover. Since winter is coming on it may be spring before you see significant signs of growth.
Thanks for the question. Please stop in again soon!
Q&A Library Searching Tips