What is wrong with my Dieffenbachia? More and more yellow leaves appearing (I've cut some of them off already). I water it once per week. It used to sit on the window 6ft Real Touch Artificial Fiddle Leaf Fig Tree in Black Pot Faux Fiddle Tree Realistic Fake Tree Silk Plant Home Office Plant Potted Etsy Customizable Elegant Artificial PEperomia Tetraphylla Indoor Faux Bonsai Rubber Plant Elegant Houseplant Silk Plastic Potted Alfama Narrow Planter