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Schefflera and most other indoor plants are often overwatered. This plant prefers to have its soil dry out between waterings, so check the soil to make sure it's dry a couple inches down before you water.

You can tell if you're underwatering a plant because it will wilt, but then will perk up shortly after you water it. Overwatered plants won't perk up after watering.

https://www.gardeningknowhow.com/houseplants/schefflera/schefflera-plant-care.htm

It may be as simple as water deposits from water splashing unto the leaves. This residue can be cleaned from the leaves with a damp clean cloth.
Plants can become dusty over time and will benefit from a cleaning. You can wipe the leaves or even give them a shower.
Place the plants in your tub and gently shower them with water. Allow to drain and dry.

If the problem persists it could be caused by a fungus or insects.

Neem Oil is a good and safe treatment for both issues. It is also safe for people and pets.

Here are some links with more information.

https://www.gardeningknowhow.com/houseplants/hpgen/how-to-clean-houseplants.htm
https://www.gardeningknowhow.com/houseplants/hpgen/grooming-and-care-tip-for-houseplants.htm
https://www.gardeningknowhow.com/houseplants/schefflera/schefflera-plant-care.htm
https://www.gardeningknowhow.com/houseplants/schefflera/sticky-schefflera-leaves.htm
https://www.gardeningknowhow.com/plant-problems/pests/pesticides/neem-oil-uses.htm

Try increasing the light your plant is receiving. Northern light in winter months is not likely enough for your plant. Indirect, bright light is a good location.
Schefflera are a tropical plant and love a warmer temperature. They actually will suffer in temperature below 60 degrees F.
Warm up the plant in a brighter, sunnier location and it will likely thrive.

Here is a link with more information.

https://www.gardeningknowhow.com/houseplants/schefflera/schefflera-plant-care.htm

Mostly grown for it's foliage, a mature Schefflera will produce flower clusters.
The flower clusters eventually will produce cascading maroon to black berries.
You do not need to remove the flowers unless you prefer to. There are some reports that the flowers can attract insects.

Pruning is easy and is a good idea to keep the plant from becoming to tall and leggy.

https://www.gardeningknowhow.com/houseplants/schefflera/schefflera-plant-care.htm

It will depend on if the roots suffered damage.
Cut the plant back and wait and see.

Yes, you can prune your plant.
This article will help you.
https://www.gardeningknowhow.com/houseplants/schefflera/schefflera-plant-pruning.htm