The plant is producing THC now that it is in the flowering stage. And i guess it is smoke-able. BUT. The buds on the plant that have the highest concentration of THC wont be fully formed until week 6-10.

SO yeah you can go ahead and pluck off what ever it is you want to smoke. It will have THC but it wont be worth it. The smell will only get better... Or worse depending on your view upon the situation.


As for the yellowing of the leaves. Get pics up asap.
imp:
Good luck!