Could you let us at least know what you're growing? A photoperiod? An autoflower? From seed? A clone?
If it's an autoflower, I wouldn't add the compost... that would probably make the soil much too hot for them... in fact, I don't like starting out my autos in anything that has ANY nutes in it... so when I grow in soil, they start out in ProMixHP... and they don't get nutes for at least 2 weeks... usually 3. And if it IS an auto, start it out in the pot it's going to finish in.... they really don't like to be transplanted at all... if you don't want to do that for some reason, you could start them in a peat pot so that it's just buried in a larger pot later on without having to take the seedling OUT of anything...
Good luck!