As far as I know, supplies ARE redistributed. Have you tried not moving the fleet for one turn? I had a raiding stealth cruiser that had totally run out of supplies, and moved a brand new stealth battlecruiser to the CA's sector and formed a fleet. It's a good thing that I did, b/c they were attacked by 4 battlecruisers immediately after (I forgot to turn their stealth armor on). When I went into tactical combat, each of them had 1340 supplies, so they SHOULD be distributed throughout the fleet.
BTW, they totally reamed the Krill Dominion's 4 BCs, and took no internal damage in the process. Plasma missiles and shield depleters can't stand up to the might of Type IV and V phased polaron beams
