Reducing max health instead of dealing damage to health pool.

So at 10:28, they are trying to fight Maokai and he doesn't take any damage, but if you look at it his health bar, he's actually losing max health. They actually reduced his max health from 2800/2800 to 1700/1700 before he started taking damage. I don't know what caused it. Maybe it was a weird bug with colossus or some strange bug with corrupting potion, I don't know. But the moment he stepped into base the potion stopped ticking, his health returned to normal.