Can you send a photo? Sounds like a fungal leaf spot. If one leaf is turning yellow I would not worry but if all do there is a problem.
As a homeowner hard to diagnose diseases, and not all are treatable. Be sure when you prune off dead leaf you wash cutter in alcohol before and after, not to spread infection. Do not stress
plant by over feeding or keeping to wet. Keep foliage dry too, and make sure its getting enough light.. they do not make great houseplants.
Also make sure you do not have fungus gnats.. they can spread
plant diseases to other
plants.