Fungus in growth chambers

Hello,

I have three Arabidopsis growth rooms with a fungus related problem. The
symptoms appear on leafs and translate in a chlorotic area surrounding a
translucent zone. Almost all plants are affected. The soil also gets
moldy and with algae even if not watered in excess and with good aeration. Did
anyone had a similiar problem and can give some hints how to prevent and solve
this two situations? And can you advise me a good website or book with pictures
of symptoms and signs of the several diseases and pests that might affect
Arabidopsis?

Thanks a lot!

Vera Nunes