The tiny white specks on the leaves appear to be either spider mites or thrips. I would say mites but either way, you need to get some Azomax, or SNS and treat the plant asap.
The bigger yellow/brown spots make me think calcium or manganese deficiency. But before treating ffor that, we need to know what kind of soil they are in, and how much(how big of a pot).
what all do you feed them. How often, how much?
What kind of water do you give them, how often and how much?
Are these plants grown outside or inside?
What temps do they live in?
Do you check the pH of your water/solution before adding to soil? Do you check it after watering, at the runoff?