Durkadurkastan!, Pathfinder founds a new chapterhouse! Options

[DisgruntledExGWS...]

That's.... rather random.

Can you arrange for them to be split again? Just to see how it pans out? Failing that, could be a good time to pull him aside, casually chat about the change in play.

I mean, let's just imagine for a moment that perhaps he's embarassed to nerd out in front of his buddy, or enjoys getting more involved in smaller games because he's seen one too many devolve into a brawl when 4 people can't decide on one course of action?

There's always the random possibility he had a sudden brainstorm, but when people shake up their playstyle I'm always keen to find out the motive.

Were I in your shoes, I would now feel a little bit more content in my GMing ability, since the issues definitely now seem to be player related. But yeah, give him a pep talk on his new style, find out what he liked if it's something you can incorporate in the future.