Yellow leaves

[SRS]

Is it normal for some leaves to start turning yellow when the plant is Budding? Do you need to check nitrogen level and how do you boost this level?

[Weed Pharma]

If the leaves are yellowing from the bottom up- you are fine as it is a normal process. Plants need less nitrogen in flower and too much will stunt growth. Sativa's have more tendency to begin yellowing at the flip to 12/12.
That said:

It would be helpful to get a pic of the leaves and the entire plant, to rule out other causes.

[rockman]

What are you growing in, and currently feeding? That would give us a better idea of what to recommend. And pics of course. Thanks