Your humidity level
Generally, Scheffleras will thrive when placed in medium to bright indirect sunlight. When exposed to direct sunlight for too long, the foliage will burn. While Scheffleras can adapt to low light areas, their growth will slow. Too little light can result in yellowing leaves. Take note of the light your Schefflera is receiving and move accordingly.
Weakened or stressed Scheffleras become more susceptible to insect infestations. Sap-sucking bugs like spider mites can drain your plant of moisture. This problem quickly manifests itself by yellowing leaflets and fronds. Scale, mealybugs, and spider mites occur frequently in indoor conditions. If not killed early on, these small pests proliferate and move all along frond parts into nooks and crannies. The piercing mouths of the insects exhaust your plant and accelerate yellowing, especially if your Schefflera is already unhealthy from poor lighting, a nutrient deficiency or improper soil moisture.
Some yellowing is natural
Is your Schefflera pushing out new growth? If there is new growth on your plant and the yellowing leaves are older, particularly at the bottom of the plant, this yellowing is natural. Your plant sheds its old leaves and sends energy to new growth.