Thank you for your question. An accurate diagnosis would require examination of the leaves under a microscope. I don’t know your location, what diseases yo have in your area, or what care you have taken of your plant. Best I can do is to refer you to some articles so you can compare symptoms. Bacterial: https://extension.psu.edu/philodendron-diseases Bacterial, fungal and abiotic: https://hgic.clemson.edu/factsheet/houseplant-diseases-disorders/ Hope these are helpful. Good luck!