Help! My seedlings are dying!?

My wife and I grow a hot bed every year. After planting all the seeds we need, and after they grow up to the transplanted stage, we plant all we need in the garden and sale the rest. Hot beds usually grow better outside, where real sunlight shines on them, but you can grow them inside, make sure the heat doesn't dry your hot bed out. Don't plant your seeds too close together and don't put a lid on them through the day, except getting them starting to grow, and in cold times where the cold would hurt them, but raise the lid about four-inches when temperatures rise to safe conditions. After the plants emerge from the ground, and if weather permits, take off the lid and let the night mist get on them at night. We plant our seeds in Miracle-Gro potting soil and use Miracle-Gro mix with water once a week, but water them lightly every other day or as needed (make sure your hot bed can drain well). When the plants get about two-inches high, we spray them with a vegetable bug spray to keep the bugs from eating them. After the plants get at the planting stage, around four to five inches high, we transplant them in our garden. My wife and I wish you all the success in the world and God Bless.