I had the same problem with 2 of my plants.. no idea what it was i will try to post a pic tommorow of what happens when you ignore this problem for a while. One of them managed to pull through it but the other died.. thankfully the survivor is pulling through and has stated new growth.. anyway buddy the my solution is just leave it for a while if it continues to worsen then give the plant a very light flushing and it should clear it up... my guess its over nuteing but just leave it for a while as the flush may not be necesary.. ive had a succesful crop with a plant that had this problem.. and it turned out fine ( and female!!) anyways bro good luck!