The leaves turning yellow does not mean the buds are ripe. You have to check the status of the trichomes for that, or look at the hairs as they go from pure white to brown or orange. When production of fresh white hairs at the top of the bud slows, and the hairs are turning brown much faster than they are being replaced, you are getting close to harvest.

Don't give a flowering plant N just because the leaves are yellowing! You don't want it resuming vegetative growth.

The yellowing is natural, but sorry cannabecea that looks like you have a light problem and the yellowing is from not enough light getting to the plant. The leaves should not be that yellow in that early a stage of bud development.