AsicMiner USB Miner issue

[rileyA.]

So all of my miners are still mining away so I am not TOO concerned, but the green led lit up the other day on one of the usb sticks. It is fully illuminated ALL the time. I look at BFG miner and all the miners are working still but the one in question is hashing at 287Mh/S instead of the others which are in the 330's.

Any ideas what could be the problem. They have been hashing without issue for OVER 6 months.