Yellow buds

could be nute-related -- too much p or k has chlorosis at the top. You'd be able to cross reference other symptoms of each with a simple leaf symptom chart. Doesn'tlook like it started lower on the plant first? so that eliminates mobile nutes like N. The spacing of the leaves at the top makes me think you have a bit too much light, possibly. A little chlorosis is fine, i'd say that's a bit beyond that what you ever want to see, once you get a handle on your grows with more experience.