Its completly normal for the leaves to turn yellow due to the fact your at the end of flowering. Although for the buds to turn yellow also this is abnormal. What strain is it? And look at the little trichomes ( hairs) and when htere 75 percent darkened up then thats when you know to cut it. It wont hurt to cut a few buds off that are ready either. It makes more light and room for the others. The light could be the problem thats glowing your buds yellow so make sure there ready before harvestin.