I'm only guessing, but I wonder if your sowing medium could be too moist?

I haven't found seeds mildewing or molding to be an issue but my technique is a little different than yours...and I don't use a commercial fungicide.

Seeds from my own plants are sown within a month of harvest, pots are left outdoors. Seeds that are not from my own plants that arrive dry are soaked overnight, then put into a 2x3" zip lock of sterile moist (like a well squeezed sponge, not soggy) sand or sterile moist vermiculite. The bag doesn't need to be filled, just a teaspoon or two of medium is plenty for 20-40 seeds. The bag is dated and stays on my desk for 6-8 weeks.

When the moist warm period is completed, I sow the seeds (4x5" deep pots to allow for root growth), top pots with grit, and either place them outside, or wrap in saran and put into my refrigerator.

If you are ordering seeds, you might ask what year they were harvested - it should be close to the time that this years seeds are available.

Thank you for your help. I think I will buy a few plants to start out, and maybe I'll have better luck in the future with fresh seed from my own plants.

I just saw this post so this won't help you this year but next year when you put the seed in the refrigerator, use only vermiculite in the baggie with the seeds. With damp (not dripping wet) vermiculite I've never had any mold or mildew problems. I also put the seed in baggies with vermiculite for the warm moist stratification period. Then just transfer the baggie to the refrigerator. They germinate in in the refrigerator in the baggies. When I see green leaves I transplant them into pots.

I'm not certain but I think 18 month old seed may be too old for good germination. I've sown seed the January following its ripening and gotten good germination but eighteen months may be too long. The longer the seed is stored dry the more dessicated it becomes and at some point viability is lost.

Thanks Loretta! Next summer I will try again with just vermiculite.