Firstly, not to be argumentative but I believe that is nitrogen deficiency as shown on this chart. But overall this looks like a healthy plant.
When and how much too feed is variable depending on what medium she is in, what type of soil, what additives if any have been used, what nute system you are using, etc.
Best 'advice' I can give you or anyone is to read, study and find your own answers. Then you need not worry about conflicting opinions from other posters. Lots of great info on RIU and some great examples and knowledgeable folks. But, at the end of the day it is your grow and only you can control what happens with it.
Good Luck and Great Growing