Going to need more information, mate. Fill out the troubleshooting form. A photo of the whole plant would help too.

Just from the photo it could be nute/water splash. Those beads of water act like a magnifying glass under HIDs. It could be wind burn if the fan is too close. It could be a pH thing. It could be a nute thing. It could be a pest problem. (check under your leaves) That troublehsooting form will help people to help you. :thumbsup: