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.
Willie Smits: Village Based Permaculture Approaches in Indonesia (video)