Even in Phoenix, the daylight hours shorten in the winter and lengthen again in the summer. This is what we're referring to when we're saying that light impacts their egg laying. It's the photoperiod length, the total amount of continuous light exposure in a day, that triggers the hormonal releases that cause egg laying to stop or start, not the amount of sunny days versus cloudy days or anything like that.
Pullets, that is female chickens under a year old, very often skip having a molt in their first winter and keep on laying through to their second year, but it's not unheard of for pullets to quit laying and have a molt in their first winter, either. I've had a few here over the years that did just that as well. They are perfectly healthy birds, they just opted to take a winter vacation instead of working through the holidays, so to speak.