It's void...

Grounded is on you're most likely getting killed while jumping, no?

There's a glitch about if you leave an activity while joining another all the skulls get added together. So say you're in heroics and join a nightfall lobby it loads you in with all the skulls. I've only been able to do it once, I was in nightfall and the reset happened and got invited to that weeks nightfall, and I loaded in and had all the skulls from both nightfalls. Since heroics are solar this week maybe that's what happened to you