It’s nutritional deficiency. do you fertilize it?

id define and insure all cultural variables are proper.. before jumping to bugs ... if ever ...

how long potted.. how old is media.. do you flush the pot when watering.. do you fert .... etc.. etc.. etc ...

you are going to have to give us info to work with to get to the bottom of this ...

ken

@ken_adrian Adrian MI cold Z5 and @petrushka (7b) I live right on top of the equator, these things grow like weeds and will flourish right where you put them. Aroids would grow in the compost bin if you uprooted and threw them there, such is our climate, so this is quite a new thing for me. I have grown Anthuriums for their flowers commercially, so not new to aroids. I have planted my philodendrons in a rich mix of loam, perlite, green and brown leaf mold in equal parts. Fertilizer formulated for foliage plants with NPK 30:10:10 (that has added micronutrients) very weakly each time I water. After posting this, i started spraying neem oil and soap solution and the new leaves are distinctly better. Wouldn’t that speak for a bug problem? i avoid pesticides because i have three dogs.