No, not at all. It will be 4 degrees warmer in the coop anyhow, as a rule.Fully feathered chicks don't mind those temps at all. These Autumn weeks with their up and down temperatures serve nature's purpose. Winter is coming with really cold temps. To prepare, nature has these nights which spur the chicks on to full, thick feathering. Their feathering responds to this. If it were still 90 in the day and only 74 at night, the feathering would be much slower.