Soil molds?

Hello there,
I have a question about a white and/or grey mold growing on the soil surface of my Arabidopsis pots. The growth room is a bit improvised but the best I have currently, meaning: it is a normal room with air-conditioning. The temp. is set to 22C, the humidity is not adjustable (I measured it: 42-43%). There is no air circulation from the outside (I was told so by the company who installed the air conditioning system). So, I am trying to grow Arabidopsis on soil (75% white peat, 15% mixed peat, 5% clay, NPK 14-16-18, pH 5.5-6.0, salt: 0.9 g/L), under the following light regime: 10 hours day, 14 hours night. The soil is mixed with Perlite in the ratio 3:1 or 2:1 (soilerlite). The molds turn up irrespective of the soil treatment (autoclaved or not). Initially, the growth room was disinfected by Buraton (a mixture of ethanol and propanol), and UV-ed for 72 hours. Currently I am trying to fight the molds with some Bayer fungicides available in Croatia (Antracol, Baycor and Bayleton), but these do not help well enough. So, if anybody had similar problems, I would appreciate some piece of advice.
Thanks,

Nenad Malenica