Terrified Guinea Pigs? Strange Behavior!

Question
Our pair of guinea pigs (1 neutered male, 1 female--siblings from the same litter) are behaving very strangely and we would like some quick advice, if possible, please.  The strange behavior began yesterday evening when Jewel, the female, began stampeding furiously around the cage until she finally ran into a wall and seemed to calm down.  This evening she and her brother, Jasper, both stampeded furiously around the cage (much more frenzied activity than even their most joyful normal stampeding) just before feeding time.  We checked Jasper (being the easier of the two to catch) for mites or other signs of illness/infestation and could find nothing.  After putting Jasper back in the cage we resumed our usual feeding prep.  Both pigs are crazy about their veggies and are usually at the nearest corner of the cage, "wheeping" like mad and even chewing at the bars of the cage in their eagerness to get to the veggies.  Today both pigs stayed in the opposite end of the cage with their noses in different corners, and they still have not approached their full-to-the-brim veggie dish.  This is absolutely unheard of!  They are always very eager eaters, as their large size (nearly 3 pounds each) clearly shows.  The veggie dish is still untouched and it's been nearly an hour since it was put down with fresh veggies in it.  Jasper and Jewel will be 2 years old in September, and other than a minor mite infestation about a year ago, have never had any health problems.  Can you tell us what might be wrong with our seemingly terrified guinea pigs, and what we might do to help them?  Thank you very much.

Answer
Were they ever treated for the mites with Ivermectin, a shot given under the skin? Even if they are not showing signs of hairloss the can still have mites, their behavior seems to indicate mites. The biting irritates the skin, especially when the weather warms up, then the pig runs around like crazy because of the itching, this can also cause them to go into seizures. Another reason could be fighting, have you heard them chattering their teeth towards each other? Guinea pigs when fighting might lash to the side, stand beside each other chattering their teeth and run from each other. I have some information about mites and treatment on my website http://woopets.bravehost.com . If you have any more questions contact me.
Brittany