I planted several plant seeds (watermelon, herbs, etc) in individual, small containers and let them root and grow for over a month. My watermelon plants were about 5-6 inches tall when I planted them outside in a raised garden bed with fresh container soil and manure mixture, which is what I do every year. The next morning, all of the watermelon plants were dead. They looked dried up, but I watered them very well and planted them later in the day, so it was not from too much sun. I was careful about their roots when transferring, and they were planted into the exact same type of soil. Any ideas on what could have happened?