My toddler got his two upper front teeth and two lower front teeth in pairs at the same time. But since then his teeth have been coming through haphazardly - he had one come through in his upper jaw (third from front) and then one in his lower jaw (second from front). I read that they’re meant to come through symmetrically and in pairs, so am a bit worried. He also has a big gap between his front teeth. Is this something to be concerned about?