I just want to add some other things which are very important to take into consideration, firstly;
a. Did you actually ever witness any agression/harrasment from either the barbs or krib towards the corys?
b. Tattered looking fins are a classic symptom of finrot. If you never witnessed any agression between the barbs and kribs towards the corys, its completely reasonable to assume that the fin damage was not from bullying but actually from finrot. Finrot can also come about very dramatically in fish sometimes- one day the fishes fins look fine, and the next day they have big chunks missing out of them.
I'd also like to add that you should never touch fish with your hands because;
a. The temperature of your hands is much hotter than that of the fishes body temp and the heat from your hands is very stressful for the fish to endure.
b. Fish are covered in a protective slime coat which protects them from things like deseases and parasites. The slime coat however can be very easily damaged from physical contact, and when damaged makes the fish in question much more vunerable to attacks from deseases/parasites etc.
So you shouldn't handle fish with your hands as you can easily damage the fish from handling them- its also another reason why you should never net fish unless very nesarsary, and if you have to, the net you use should be of a very fine material to help reduce the chances of bits of the fish getting caught or scratched on the netting. Ideally, the best way to move a fish is to catch it in a container or bag full of water so the fish is not forced into contact with the sides of the container and can swim about freely in it.
