Not sure if it's the correct Exchange but I hope so.

I recently started a new hydroponic culture with an AeroGrow Aerogarden Harvest Slim. I put it in my house that doesn't have a good air circulation but bad neither; it's a standard room of ~40 square meter.

After about a week I was able to see the germination results, really small but visible. Suddenly, from day to night, checking my hydroponic I saw all the sponges and pods totally covered by mold.

The days before I checked the pH and it was correct, nutrients too. What could the problem be in that situation?

I thrown it all away and I would really like to try again but I'm not able to understand the problem. How can I investigat about it?