Some dap.
You must be registered for see images
hahahahahaha too funny.
But seriously.
I think they gave him a part of their "soul", not chakra. Or in other words, they put a part of themselves inside Naruto so they couldn't be sealed/used by Tobi any longer. When Tobi tried to take back the Tailed Beasts he wasnt able to, and I believe this is because they are now inside of Naruto somehow. Kinda like how Madara can't take control of Karuma b/c its in a Jinchurriki. The other tailed beasts' souls are now a part of naruto since they taught him their names. This was done to weaken Tobi as now he can no longer use their power. But I'm not convinced they ALL gave him some chakra. Not yet atleast lol.
-gHost Senju, K.U.S.H. Sage