Were the chickens more confined when your were recently working such longs hours? Boredom, not getting outside to roam, overcrowding, too much light, too hot, all can be reasons for feather picking. Having your roosts where they cannot reach others might help. A 20% all flock /flock raiser type feed, at least 4 square feet of room per chicken, and letting them outside to roam can help. A small $10 can of pine tar from TSC painted thin on the pecked areas keeping an inch away from the vent would be a good way to stop it immediately. It is sticky, stinky, and has healing properties. The Nustock works too. It should be stopped soon because this can lead to deep wounds or vent damage. Here are a couple of articles to read:
https://en.m.wikipedia.org/wiki/Vent_pecking
https://extension.psu.edu/poultry-cannibalism-prevention-and-treatment
https://en.m.wikipedia.org/wiki/Vent_pecking
https://extension.psu.edu/poultry-cannibalism-prevention-and-treatment
