Leaf disease

[MarlynnMarcks]

My fall tomatoes are doing extremely well and already have some flowers. I am in South Florida and have seen something I never had trouble with growing tomatoes in Michigan. Almost overnight 1/3 of my healthy plants became covered with a white almost furry substance. The leaves cured up and the tomatoes looked dead or dying. I threw them away but am afraid the same thing will infect my remaining tomatoes. Does anyone know what it is and how to get rid of it?