Usually, this is due to underwatering, a lack of light, insufficient humidity, or pests ... dealing with a fungal leaf spot ...
Indoor temperatures for philodendrons should be kept at around 65 to 70 degrees [Fahrenheit]. Common problems: While pests and diseases are uncommon with philodendrons, bacterial blight ...
If you notice pests on your plant ... Fungal leaf spot diseases are common in philodendrons and can be easily passed from ...