I received a Monstera deliciosa some time ago and I'm wondering if it doesn't show signs of root rot. Most of the leaves seem unaffected but one of them has rather big dark spots on it, another one has one small dark spot and there's also a dark stain on one of the stems. In addition to that one of the young leaves is yellow. I've heard that one has to fight root rot immediately after the first symptoms have occurred to maximize the chances to save the plant. Please, examine the photos that I have attached and tell me if I should worry. Thanks in advance for your help.