One of the reasons you want your seeds to germinate quickly, is the fungal disease, damping off. This disease will kill your seedlings. If you notice some white stuff on the top of your seed starting mix, this is an indication of the disease. You can see the seedling is the upper left has thinning on it's stem which is making it start to bend over, that is damping off. The fungus will kill the seedlings and it can spread. If you notice the white on top of the soil, or the thinning of the seedling stem, you should cut that cell out and throw it away, immediately! Don't put it in your compost pile; never put any diseased material into your compost pile. If you take care of what is infected, you have a good chance that the rest of your seedlings will be ok. To avoid this disease, make sure your seedlings have enough light; which means a good 14-16 hours a day. Make sure they have enough heat (use a seedling heating pad if your place is chilly). Keep them watered, but don't over water, over watering will help the fungus as well. I've had this fungal disease from time to time, not very often and it doesn't usually get to all my seedlings. I keep watch for it, and try to make sure my seedling have what they need to avoid this disease.