Boss health boosts over a million or so

How come when i’m trying to grind for an item, (now that drops are mega nerfed) that i’m shooting the boss, and in one game, i melt it, the next 2 i’m doing 10%damage and it takes 10 minutes? how does the boss suddenly get like a million extra hp randomly?

Are you playing on a Mayhem Mode?
They have random modifiers, you can check them in your map.
They can penalize certain damage or weapon types and if those penalties stack up can get really crippling.

yeah, ok. kinda makes sense, i guess i forget to look every time i reboss

Happened to me. One farm I melt the boss. Next game I’m the one getting melted.