If the spots on the leaves are very, very small and kind of look like pepper, this to me sounds like spider mites. Do you see any spider webs around the leaves? Especially on the underside of the leaves? If that's the case, you can find many sprays that will deal with spider mite. In fact you can make your own if you like. There are many different recipes out there, but it basically consists of water, rubbing alcohol and dishwasher soap. As you can tell from those ingredients, there are sprays available that do not require harsh chemicals to help mitigate the problem. I hope this is helpful information. Let me know if you have any further questions. Cheers...Dr. Robby