Why is a 9 day old seedling in a 3 gallon pot? You are practically asking for watering problems by using a pot that is too big for the plant size.
I start with a pot that weighs 150 grams dry, then transplant to a pot that weighs 400 grams dry, then 1200 grams dry, until finally I end up in 3 gallon fabric pots that weigh 4000 grams dry. I use a scale to weigh the pots to be sure I don't water too soon.
If you use a pot too large, then you cannot water properly because if you soak a 3 gallon pot with just a seedling, that pot will still be soaking wet after 5 days. The pot needs to be small enough to dry out, otherwise the roots will never get enough oxygen. When you water to soak the pot, you are actually forcing fresh air thru the dirt, after the water dries out there is fresh air left. If the roots never get air, they will rot, or at the very least they will retard new growth.
You need to use pots only large enough for the plant to use all the water in 4-5 days, and replant as needed. You will be rewarded with fast, healthy, vigorous growth. Do not make the mistake of starting with your finishing pot.