Gothic international. This is THE look starting late fourteenth through to say, 1450.
Take a look at some Gentile da Fabriano, or Jacopo Bellini - these sweet round blonde faces are what you see. It's a bit less prevalent towards Florence, because of the Giotto-Masaccio continuum, though even Masolino... too, look at Fra Angelico, though he and Benozzo Gozzoli are kind of the end point of that particular tendency. I personally partially relate it to Medici visual politics towards a style that was never particularly deeply entrenched in Florence anyway, not like it was up in the princely North (and the sweet oltr'alpini faces). It is a "courtly" style.
-sorry, I usually don't come 'round hereabouts but the dissertation possessed me, as it occasionally does, to respond
-saba