Does brood examination show something suspicious?
If a beekeeper sees anything odd about brood or the bees in a hive, s/he may leave the hive tool used to inspect that hive on the inner cover before putting the outer cover back on. The next time opening that hive, the beekeeper is reminded that this is the hive under suspicion and is reminded not to use any other hive tool in that hive. Dedicated hive tools are an important strategy to avoid cross contamination of hives if a disease issue, particularly of the broodnest, might be active. Many broodnest diseases respond to good hive management and the improving weather in spring. Chalkbrood is a good example of one that usually self-resolves under such conditions. However, even if that is true, why transfer any such disease organisms to another hive, adding to its stress?