Ctenanthe lubbersiana? That patch with the darker spots looks fungal to me. I would check the roots, if they look healthy not dried up or rotten, I would get a fungicidal spay like captain jacks. Applied at night to avoid burning leaves. Could be an airflow issue as these plants like to be evenly moist and in relatively higher humidity or they crisp up along the edges. Without some good airflow fungus can spread.
Ctenanthe lubbersiana? That patch with the darker spots looks fungal to me. I would check the roots, if they look healthy not dried up or rotten, I would get a fungicidal spay like captain jacks. Applied at night to avoid burning leaves. Could be an airflow issue as these plants like to be evenly moist and in relatively higher humidity or they crisp up along the edges. Without some good airflow fungus can spread.
Here is what the product looks like:
https://www.amazon.com/Bonide-BND022-Pesticide-Organic-Gardening/dp/B007CRG4CW/ref=asc_df_B007CRG4CW/?tag=hyprod-20&linkCode=df0&hvadid=692875362841&hvpos=&hvnetw=g&hvrand=1338027126158313153&hvpone=&hvptwo=&hvqmt=&hvdev=m&hvdvcmdl=&hvlocint=&hvlocphy=9033326&hvtargid=pla-2281435179338&psc=1&mcid=60626137824b3893b333367f3328b587&hvocijid=1338027126158313153-B007CRG4CW-&hvexpln=73&gad_source=1