I've got six bags of fully grown blue oyster mushrooms grown on starbucks coffee grounds.  While they are fruiting they aren't forming properly.  Can I get some suggestions?

Nice close up pic Ben. Added this to the soil forum also. Some serious mushroom info there too. Hope you don't mind. Welcome to permies.

If all you had for substrate was the coffee grounds the issue is mineral defect, usually you want to have the main part of the substrate wood chip based with coffee grounds added in (2/3:1/3) with a little rock dust mixed in for well formed fruits.

I like to add gypsum and some woody material (spend hemp straw form the gerbils and the like) to the spend coffee grounds. What is you humidity? I got a similar look when I had too dry conditions in the room.