Broad mites can infected a schefflera. However, is often goes unnoticed until severe damage has occurred. Initial symptoms will be downward cupped leaves with a serrated, puckered, and stunted growth. If you have mites you will need a miticide to kill them.

Another possibility is that the schefflera has been infested with thrips. A schefflera with thrips will have leaves that are curled or distorted with silver-gray scars or calloused areas. If you have thrips you will need an insecticide to kill them.

In both cases the damaged leaves will not return to normal and will need to be prune off of the plant. You can find the products you need at your local garden center and nursery. Once you kill the invader, your plant should recover. Please keep me posted. If you can determine what is wrong, send me an up-close picture of one of the leaves from the top and back side.