schefflera losing leaves

Hi: I have an indoor gold capella schefflera plant, and its leaves are falling off quickly. I water it once a week, place it near a window with bright sunlight. The leaves falling off are kind of brown and withered. Could someone tell me what I am doing wrong? More watering? I also have another schefflera plant (just green leaves). This plant is placed near the above gold scheffelera, receives the same watering schedule+amount, and it thrives!!
Thank you, Minh
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