What is causing this discoloration on my Schefflera's leaves?
It's like a water color effect. There may be embedded bugs in some leaves.
This plant is deficient in a number of chemicals. Some people say 'nutrients' but the chemistry plants need, fertilizer is not at all food. Plants need these chemicals to make their own food for energy, to grow, to root and to make flowers and fruit.
This is a deficiency in Magnesium, possibly. Fertilizing gets far more complex, a lot of symptoms depict a number of different elements missing and or being hampered by pH of the soil.
We need to know what you have added. What was in the soil you used when you planted this Scheffelera? Is this in potting soil? Do you have a pH meter of any kind? Are these leaves on the bottom of the plant or are they on the top of the plant? Newer leaves or older leaves? What are you watering methods? Growing plants is very much a chemistry experiment, especially when plants depend on the human's input completely for growth in a pot.