Hi, can anyone let me know why the carolina Cross watermelons are so hard to grow?

This is the first year i tried to grow Carolina cross watermelons. To make it short and sweet, i got the seeds from burpee and planted them in a small green house. Out of 25 seeds 1 survived. I prepared the soil with cow manure and blood meal and some compost before planting. Made sure i watered them but yet they all bellied up but one. Whats the secret to getting these plants to grow?