Are you using the seed planting trays with the individual planting cells? The dreaded damping-off fungi are everywhere so even if you use sterile soil and fresh water you can have this disease attack your seedlings. The only tip I have is to make sure you have no open, empty patches of soil. This is why planting the seeds in little cells keeps them healthy - you can buy the planting cells for your Aerogrow rather than try to sprinkle seeds directly onto the soil. The theory is when soil is filled quickly with roots the fungi can't grow as well but when damp soil sits around with no roots filling up the space the fungi grow instead. This is why seedlings do best started in tiny pots, then moved up to larger pots just one pot size at a time. Good air circulation should also help and so a bit of wind from a room fan will be a good preventative measure. You might want to try a different type of seed - some varieties just are more prone to fungi than others. Keep trying and Keep Growing, Marianne Binetti