Yes. Way too much.
I use one or two for maybe every square foot of substrate.
OP: Doesn't matter if you disturb your substrate or not, once water hits the osmocote? It all starts to breakdown and become available.
Isn't 12 capsules of the stuff too much to add? How long has this tank been running?
If I was to supplement the substrate with gel caps, I would use 3. (Left, Center, Right)
I can't figure out which one is the gourami. Too early in the morning for me.
Any fish with weird bumps, spots gets removed immediately for observation.
Good luck catching the suspect.