Answer: Dieffenbachia can drop leaves for many different reasons. It hates drafts and needs a relatively warm room temperature, if exposed to cold it will defoliate. Over watering or underwatering can also cause it to drop leaves. The soil should be slightly damp, never soaking wet and not commpletely dried out. A fairly common problem in winter is too cold a room temperature combined with over watering. Make sure too that it is receiving enough light now that the days are shorter; it tolerates relatively low light, but it does need some indirect light. Also try to increase humidity around it if you can. A pebble and water tray or a humidifier can help.
Anthurium is really a tropical plant, think jungle conditions: warm room, high humidity. Browning on the edges is often either due to over fertilizing or dry air. This plant is not an easy one to grow at home unless you have the right conditions for it, so do not be too frustrated if it does not do well for you.
I hope this helps.
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