houseplant problems

I have a corn plant, a ponytail palm plant, a rubber plant, a chines
evergreen, and a dragon tree. I noticed about 2 weeks ago that my cor plant was having problems. A few of the leaves started turning fro green to yellow to black. Then about a week ago I noticed a white fil on the plant by the stems where the leaves start. I also saw that th new growth was turning brown and dying when the leaves were only abou an inch long. most recently there are like light brown spots or strip on some of the leaves. I thought it might be root rot but then noticed my ponytail palm suddenly had a white film on the stems wher the leaves come out. So i looked on the internet for a while and now think they must have some sort of pest or fungus. Im adding pictures s you can see exactly what im talking about. What is wrong with them? And how can I fix it
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