It is very difficult to control fungal infections once they've taken hold--prevention is the key. You may try temporarily moving the pot into a less humid place, spray the surface with a fungicide (e.g., Captan), let the medium dry out just a bit, and pray.
As for the green stuff, it is likely algae which can cause problems depending on the species and amount.
In terms of prevention: If the water at the bottom of the terrarium is stagnant, this can promote the growth of water molds/fungi. Sometimes this presents as a "film" or thin layer covering the surface of the water. In any case, in the future you may want to remove most of the water from the terrarium and add just enough to keep the medium constantly moist. You may also wish to apply a quick spray of fungicide (e.g., Captan) to the surface of the medium before dropping the seed, though I've never had to do this myself.
Your method of germinating seed is similar to my own, except i use a plastic tray instead of a terrarium, add just enough water to keep the medium moist, and cover the pots with transparent plastic wrap.
Hope this helps.