Some thoughts...
1. Are all the animals spayed and neutered? I assume so, if not get that done ASAP.
2. Introductions should really be done slowly, with the new animals confined to a space where the old cannot get to them. They can sniff each other through the door and get to know each other that way at first.
3. Their scents may be a problem. Try to switch out blankets/beds they sleep on to get them used to each other's scents. Also you can try Miracle foaming waterless cat shampoo (or something else with a smell, like vanilla) rub a little on their fur and they will all smell like each other.
4. After a bit of a separation, try putting the new cats in a carrier or cat playpen and letting the old cat meet them this way. Then you can switch out and put the other cat in and let the new cats out.
5. You can spray Feliway around the apartment to reduce stress.
Personally, I would go back to square one and separate your cats (I keep calling them new since they are new to the house) from the old cat. Give them a break from each other for a bit and then try again. Don't rush anything. Just feel the situation out and see how they are doing as you go.
1. Are all the animals spayed and neutered? I assume so, if not get that done ASAP.
2. Introductions should really be done slowly, with the new animals confined to a space where the old cannot get to them. They can sniff each other through the door and get to know each other that way at first.
3. Their scents may be a problem. Try to switch out blankets/beds they sleep on to get them used to each other's scents. Also you can try Miracle foaming waterless cat shampoo (or something else with a smell, like vanilla) rub a little on their fur and they will all smell like each other.
4. After a bit of a separation, try putting the new cats in a carrier or cat playpen and letting the old cat meet them this way. Then you can switch out and put the other cat in and let the new cats out.
5. You can spray Feliway around the apartment to reduce stress.
Personally, I would go back to square one and separate your cats (I keep calling them new since they are new to the house) from the old cat. Give them a break from each other for a bit and then try again. Don't rush anything. Just feel the situation out and see how they are doing as you go.
