Need Awnsers!!! Brownish stem

Hey stoners and stonets I am in my first grow I have one plant that is about 2 weeks old and the leafs are great and a perfect shade of green, the second pair of leaves are coming in opposit the first pair, yet my stem is very thin and it is brown but it is light green/whitish in the middle of the stem I use bottled water to water it so I dont think it is the ph levels plz help I dont want my first plant to die on me! and to be honest idk how much to water it I have been giving it a lil bit everyday about a 1/4 cup of water a day so idk plz help and thanks!!

sometimes the stem does go a brownish color, the base of the trunk on my plant is still brown, though it turns green at about the 2nd node up.

Make sure you dont water it too much. It doesnt need water every day when its that young. Make sure you let your soil dry out a little every time before you water it.