One budgie pair is fighting with other pair
Please help! I recently (less than a month) bought a pair of budgie (adult). I placed them in a cage of size 18X24 inches. as they were getting bored, I thought of getting another pair to give them company. I bought the new pair today. The new male is adult while the female is semi adult. The man at the pet shop told me that they formed the pair recently. After I got them home, and placed them in the cage, the new male started attacking my old pair. He also attacked his own partner. No matter how much I wanted them to stop, the new male doesn’t stop and keep attacking the other birds. What to do? Is it normal? Will they ever stop fighting? Please help.