Before you extract the Chains in your Drum Rack into separate chains, make a note of the volume of the track the Drum Rack is in:
When you extract a chain, the volume of the new track will be set to zero. In the example above, this means that extracting a chain from this Drum Dack will result in a volume increase of 3dB for that chain.
After you’ve extracted your Drum Rack into separate tracks, select them all and use the Group command to group the individual drum tracks together:
Now set the Group track’s volume to the volume of the original Drum Rack.