Probably too much water--try keeping things a little drier than you have been. You don't want to let the seed starting mix dry out, but it doesn't need to be dripping wet either. You might also try putting a bit of hydrogen peroxide in the water you use, and sterilize the mix you're starting the seeds in (google for instructions on this--you can do it in your oven or your microwave)
Another suggestion - leave the baggies open to allow some air movement. If you are sealing them tight, you will get 100% relative humidity which is sure to add to your problems. When you are germinating and you cover your vessels with plastic (either bags/ tray covers) you want to see only a little bit of vapor condensing on the plastic. If you see large drops or water dripping down the sides of your cover it is too wet and you need to vent the container to release some humidity. Seeds don't need near the moisture you think they do to germinate.
A side note - the fungi you are seeing is adventitious mold and is not plant pathogenic. It is however a very good indicator that you are too wet as ecrane indicated. The mold you are seeing is from spores that are present everywhere and will occur on every growing media whether it is sterilized or not. It will always occur if moisture is too high. The cure is lowering moisture. Peroxide will knock it down, but it will come back if you don't lower the moisture.
I also used to have damping off, algea or even mold. Wet soil surface. I could never get enough water OUT of the soil to let any air IN.
I'm not a fan of any commercial mix or doo-dad that is mostly peat. The ones I've seen have very fine peat - almost powder.
Where's the air space? If that fine peat ever gets as much water as it can hold, no air gets in for weeks. Seeds need oxygen!
I think a seed-starting mix should start out much more coarse than commercial peat mixes or pellets are. If I were to amend a comemrcial peat miox with grit, coarse perlite and screened medium-coarse pine bark, I would use 85-90% amendments and 10-15% peat!
so, instead, I start with medium pne barj mulch, screen away as many fines as I can, pick out some big pieces, add grit, and then decide whather or not to add a pinch of Jiffy-Mix.
I agree that a good germinating mix should contain plenty of airspace. I use Premier ProMix BX and, as shown in the picture, I add 5 cups of Perlite to every 5 quarts of mix to increase the aeration of the mix. The Premier ProMix BX already has some Perlite in it, but not enough to suit my taste.
Coarse Perlite is good. Crushed rock that coarse would be pretty heavy.
One thing that I especially like about well-screened shredded or chipped bark is that the chunks are elongated. I think that being 3-4 times longer tyhan they are wide makes an amendment much more effective at creating air channels for oxygen to diffuse into soil.
And, since bark does absorb and transport water like a straw, longer shreds are effective at wicking water up, down and sideways.
Plus, it's about the cheapest amndment there is, if you do the screening yourself.
I wish I could find a few square yards of 3-per-inch galvanized hardware cloth!
2-mesh is too coarse, and 4-mesh is too fine.
I've been looking for 3-mesh, or 3/8" "galvanized woven" at stores for some years.
I have found a few online $pecialty $ource$ for any kind of mesh or pierced sheet that my bank account can't afford.
If 12"x12" were any good to me, I would use MSC Direct's plain steel offerings, althoguh I happen to know that they rust VERY quickly.
Practically, I'll continue playing multiple-pass games with 1/2" hardware cloth.
I've thought about trying to "accordian fold" a small piece of 1/2" to make the square holes "diamond shaped", in effect reducing their size.
Or stacking 2, 1/2" sheets on top of each other, perhaps with a very slight offsett, just to make a "slower" seive.
But I currently have 1-2 cubic feet of the last batch I made, leftover! This violates the idea of using fresh clean (if not sterile) mix each year. But I haven't seen ANY damping off since I went to pione bark, and "ignorance is bliss".
I have progress to report :):):)
Im sure I planted them WAY too early - but I can always put some in the ground later as well. I have plenty.
Luna & blue pumpkin have sprouted nicely and are about an inch tall already. I noticed them yesterday and since then they have taken off! :D
Rio Grand Toms are starting to pop and the cinnamon basil.
I am SO excited! What do I do next?? LOL! I've never gotten this far before...
Considering your location and hardiness zone, I would have to agree with you on that. Pumpkins grow too fast to keep inside for very long at all. I kind of doubt that it is even worth trying with them. The tomatoes might be worth trying to keep going until it is safe to put them out. Do you happen to know what your "safe no-frost date" is?
Another possibility is some kind of enclosure that you could put over them in the garden to protect them from frost, so that you could set them out before your "safe no-frost date".
For the time being, I think you need to be finding some bigger pots to re-pot the tomatoes in, and a good light source for them, like a very sunny south-facing window and/or some serious fluorescent lights. And they will need some sort of plant food.
I agree with Zen, you might as well toss the pumpkins, I doubt you'll be able to keep them for the 6-10 weeks necessary before you can safely plant them outside. You should be fine on the tomatoes. You will need to step them up in pots as they grow, keep plenty of light on them and keep them cool/cold. Rather than putting them in a window, I would recommend moving them to your basement to keep them cool and putting them under lights for about 16 hours a day. Cooler temps will slow growth and give you more sturdy tomatoes esp. with the lower light levels.
The same goes for the other plants you have germinated, cooler temps with fluorescent lights are best for them.
Pumpkins should be started only a week or two before you are going to plant them out. The only benefit to starting them in pots is to keep birds/squirrels from eating the seeds before they germinate. If you are worried about getting mature pumpkins because of your northern climate, use some floating row cover/ plastic buckets or other protective cover for them so you can plant outside a week or two earlier than normal.