Pink cheeks. Could this be fifths disease?

Maybe. Fifth disease is a benign viral illness that is usually experienced in childhood. It is first evident with a rosy cheek appearance with mild fever, followed by fading of the extra color in the cheeks.At this point a salmon colored rash appears on the extremities and trunk. As soon as the general rash appears, it is no longer considered contagious.The rash can come and go for weeks. Rx is supportive.
Possibly. Erythema infectiousum, named fifth disease because it was the fifth most common childhood rash may be the cause, but if this persists, see your pediatrician.