Fireland's Boss respawned the next day after killing him

We did our 2nd day of raid in Firelands and we ran into an issue.

One of the bosses we had downed the first night (Rhyolith) had respawned.

Maybe this has been discussed before and has been addressed. I couldn’t find anything on this. Are we allowed to kill that boss again to continue our raid?

We called it because a couple of our members didn’t want to get in trouble.