Sounds like something that was destroying my indoor plants.

I can't remember the name of it but mum said she had some on her plants and when she took it down to the local nursery for advice they had a fit and screeched at her to get it out! Apparently it is highly contagious (if you use that word in the plant world!) which would explain the fact that it has moved on to your other plants...

Mum used and recommended for me to use "White oil" which I think is the same as pest oil as mentioned by Epacris. One dose cleared up the problem on my plant and it is looking very happy and healthy!

Hope the same works out for you.