my philodendron congo green have brown spots on almost all leaves (even the newly sprouted ones). However, the older leaves don't have the problem, and they have much darker green color as well. I doubt its a sun light issue (since new leaves also have such symptom even before they uncurl completely). Any suggestions what the causes are? Thank you!
I have had a similar problem with my congo. Best I can guess is that it might be a bacterial issue (though unconfirmed). I wiped all my leaves, front and back, with a neem oil mixture, then sprayed it often, especially new leaves as they form. It seems to have helped and I only have a couple leaves with spots now.