Well first, bala sharks can get to 13 inches, and the tank you have is to small for them, so you should either return them to the store or give them to someone. Second, when you say a pack of tiger bars, how many would that be? And finally, electric yellows have different
pH requirements than the other fish, and are very aggresive, so you may want to get rid of him to. If you do all this, you should have no problems adding 4-6 cory cats.