Multiplayer: static dungeon core health bars

In a multiplayer match when a dungeon core is attacked (any core), I as a host can see the damage increasing in the health bar, but my friends cannot. They see max hp until it's destroyed.

My computer stats (if relevant) :

Windows 7 64bit

CPU 3,5Ghz

RAM 16gb

NVIDIA Geforce gtx 970

The game seems to be more fluid when I'm the host. I do have the most powerful computer out of me and my friends (just barely).