By meat birds do you mean Cornish X, Ranger types, or dual purpose? How old are they and for how long? What is the calcium content of that layer feed? How much low calcium stuff do they eat that is not that feed, do they forage for a significant part of their food?
The risk of feeding a high calcium layer feed to growing birds is that it can mess up their kidneys and/or liver. But one bite won't kill them. It's the total grams of calcium all day and even then it is an average over several days. If they forage for some of their food the grams add up slower.
For two or three days I would not worry about it. If that is all they eat then I would not want to go much longer unless the feed was a minor part of what they eat overall.