Sometimes I wonder how these poor little seedlings make it all on their own out in the wild battling the wind and rain all the bad fungi and stuff.
Maybe the wind and the rainwater help.
I use Farfard Outdoor Planting Mix (Purple Bag) to start all my seeds and potting up. It is 7 dollars for a huge bag,(the one that feels like it weighs over 50 pounds) and never had a problem with damping off. Never bleach containers. It doesn't say sterile but I guess is has no soil like most mixes.
Don't over water, (I use rainwater), don't fertilize until they have true leaves and then a very dilute fish emulsion. Maybe Miracle Grow but I have never used it. Take them outside on pretty days or put a fan on them to provide circulation or shake them.These seedlings are a lot tougher then a lot of gardeners think they are.
I love cinnamon on sweet potatoes