I recently added two tiger barbs in a 32 gallon tank which already contained 7. The two new ones stay at the bottom of the tank at feeding time. They do not eat because the other ones eat all of the flakes before they reach the bottom of the tank. It's as if the new ones haven't understood that the food is at the top of the tank. This has been going on for the past 4 days. Is there a way to ensure that they eat ?