Well if you take a look at the pictures on my growing thread you will see some of the more lower leaves on my plants are slightly yellow and slightly wilted. I am pretty sure this is normal. because lower bigger leaves are not needed, and as its in the flowering stage it probably only has about a month left before you harvest it anyway. Just ensure that your not watering the plant to much. Also check its not to hot/cold for the plants where ever you are growing it. I may be able to help you further if you could post a picture of your plant, but if you say its only bitta yellow and wilt then i wudnt worry about it to much, as this is normal during flowering stage.