How old are they? Are they in school?
Sometimes a lack of stimulation in school can cause GT kids to shut down. It can actually trigger bouts of clinical depression in the worst cases. Without knowing any pertinent details about your kids whatsoever, my first guess would be lack of learning for too much of their time each day is shutting them down.
But it's just a guess. Nothing more useful than that. It's kind of weird that it's happening to both of them at the same time...
When did you notice the change? What was going on in the kids' lives? How are their friendships? How is their behavior otherwise? Do they seem happy? Are they getting enough sleep?
A lot of factors could go into this!
