You are doing well.

Don't try to feed it yet, and do not over-water, it will do jus' fine.
Hemp grows like a weed.
Most folks love their first grow to death.
Size is affected most by the amount of light.

Watering and feeding also depend on light.
Take away the solar energy and all else is moot, yah?
When she sports 2 more sets of leaves, start feeding with 1/4 strength nutes.

It would help to know exactly what kine soil.
If it's Miracle grow, it's pre-nuted, and you should add nothing but water for the first month.
Hemp wants to grow huge.
All we need do, is allow it to.

Aloha,
Weezard