Nepenthes in cultivation are rife with fungal diseases, often due to being cramped in small, super wet growing areas. Preventing transmission is key to success. Many fungi spread via a motile, sperm-like stage, swimming from pot to pot in shared water trays. Some common symptoms of fungal disease are overall failure to thrive, bumpy or raised areas on the underside of leaves, small growth. Soft brown spots may be caused by phytophthora, the same pathogen that causes potato blight. It’s an oomycete, related to brown algae, though its lifestyle is very similar to fungus.