ya man i had this exact problem about a week ago. i was underfeeding. went home gave them a good dose and they came back. takes about a week and will set u back a week on flowering(thats what i am gonna do) i when yellowing starts from the botem and moves up thats the first indicator. the plant is actually using the food reservs in the leaves to power its top proiety which is budding

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"i really need help,
i plan to grow weed outdoors i know its possible but i need to know how will i power the lights."

Ghost420: Thanks for the confirmation. I had ordered the nutes in anticipation of their 2 week birthday and they started yellowing exactly on the 2 week day. I had just gotten the nutes (web order) and it is recommended to brew EJ for 24-48 hours before giving to them, so I had another day to wait. I may do as you suggest and give them more time to veg, but currently, new growth does not seem to be slowing because of this.

When I was home for lunch, I checked them. The plant in the first pics is looking better and the yellowing has slowed or stopped. The second one seems to be yellowing a bit more, but I will know more tonight and tomorrow morning.