Question
My umbrella and dwarf have blacken leaf tips and then drop off.  I have them in indirect light and water them twice weekly. Help!

Answer
In my experience, the most common causes of leaf drop and browning on schefflera are related to watering and temperatures.  I do not know the size of your plants or the water needs.  It is possible that the plant is getting not enough or too much water. Verify that the soil is somewhat dry before you give the plant extra water.  It is best to water from the top so that water flows through.  Then, the flow through water should be discarded.  Sometimes salts will build up which can be detrimental, so it is important to water through to leach them out.

With the change in seasons, the location of the plant may be cooler than normal.  It may be necessary to increase the temperature around the plant or to move it to a warmer spot.  

It will take your plant a little time to recover, so don't expect overnight results.  Most important is that when new growth appears, that it appears healthy.

Good luck with your plants!
--Jen