My sons guinea pig died today,when i went into garage to feed them there was no movement.When i lifted their house the 2 of them were lying together one perfectly ok but the other motionless apart from the odd jerk.took him into the house were he died on my sons lap soon afterwards.The guinea pigs are brothers and are just under 3 years old,any ideas as to what could have caused this,48 hrs before this the guinea was perfectly healthy, happy, corn poping and active.