Yellowing leaves can be an indication of disease or pests along with the black spots you mention.
The black spots could certainly be a disease called Anthracnose Fungus. Anthracnose Fungus is not usually treated with chemicals but will proper care can be corrected.
If pests of other indications of disease are present, Neem Oil is a good treatment.
Inspect the plants carefully for any other indicators of the problem.
Check watering and remove any dead or diseased branches and dispose of.