DD is almost 3 and has slept 12/13/14 hours through the night since a newborn. All of a sudden in the last month she isn't sleeping through and waking up early. She gets exercise in the day, having a nap or not dosent make a difference to how well she sleeps, we have a black out blind so the light isn't getting in waking her up. She wakes and cries and calls out until we go in, we cant leave her to go back off as we are temporarily living with other people so can't disturb them every night. Is there a developmental stage round about this age that could be causing it?