Welcome back eggs! Are the Coro Sussex seasonal layers or was it a break from a molt?
About what age do they start to lay? Mine will turn 6 months old in a few days. The comb's been red since 4 mo old but it's winter (bitter cold with shorter days) so I'm sure that is part of the delay.
We've seen reports of your awful cold snap on the news. My girls generally slow down in the dead of winter and during a molt. Broodiness also puts a stop to production. 6-7 months is the average for laying to commence, though I have had them start at 5 . So weather permitting your girls should start anytime now.