new baby need help

Hello – new grower here. I have 5 plants, all very young. 4 are lovely and green and the 5th is showing signs of yellow on the tops of its leaves and the lower leaves are all yellow. At first i thought it was nitrogen deficiency yet now thinking it could be something else. Thanks in advance...

:welcome: Greetings groovy 420magazine brothers and sisters! Welcome to my crisis grow! :high-five: Let's catch up together and start from the beginning; :Namaste: 6/30/2016 the proud Washington State closed all of my beloved green cross Marijuana stores. The Beginning and the End of...

Yea so one of my two seed popped up. Thing is when is the right time to start to top it and how long should it veg.