Please see pictures. This is how leaves look like and they get brown spots on the lower side of leaves shown in pictures. I don't know what to do. I am desperate! Thank you for your advice!!!
Wr need a focused close-up, if possible. Any chance?
Looks like the plant is in the process of shedding the leaf. Do check for the possibility of spider mites. The lesions on the underside probably represent the natural progression of a reaction to particular cultural conditions that cause something called oedema.