The holders are probably fine to use as is, the fungus would take some time and humidity to grow on new film. It seems a little late to be using a fungicide on the film, it is already damaged. You could wipe the dark slides and insides of the holders with a cloth dampened with fungicide if you are concerned about future usage.

Oh, this is getting so funny, I feel like a brand new father, and his son has a rash... Oh my what can be done...
