They probably needed more room than that. I've never had a problem in my 55 with any of my barbs, but it's a long tank. I have two clown plecs and I have had them for four or five years. I also have four ottos that thrive.
Tiger barbs need more length on a tank. They will get cramped and exert aggression accordingly. I would go 40 long or standard 55g and go big with like 10 of them. Maybe rehome the tigers and get platinums