My 7month old son weight -7.5 kgs is suddenly very quite. He usually is very vocal, very playful and from yesterday he is very quite. He is Eating well, sleeping *more* than usual during daytime. Does not have temperature, has normal stools and urine. He is not screaming, less reacting vocally, playing on his own, seems uninterested. he seems happy but very quite and dull.  What could be the reason. Should I be concerned? The only thing that has changed is the climate. It has suddenly become rainy and cold outside.