Answer: Unfortunately, based on your description I am not certain what is happening. It might be a fungal infection, or there might be a root problem such as overwatering and/or poorly drained soil or something unusual might have happened such as accidental leaf contact with an herbicide or fertilizer granules. There are several problems such as mildew and verticillium that could cause those symptoms, for example. I would suggest you work with your local county extension or a professionally trained and certified nurseryman to identify the problem and based on knowing that, decide how to proceed. They may appreciate a photo of the overall plant and a closeup of the discoloring, as well as possibly a freshly cut sample kept cool and enclosed in a clear plastic bag. If it is something that requires a chemical control, your county extension will have the most up to date recommendations on what to use and how/when is best to apply it. Good luck with your plants!
Q&A Library Searching Tips