Is the connection limitation per IP or per domain?


I have several application instances running from a dedicated IP each (currently 5 in total). Every instance uses a User Stream to a different account, which it scans, and sometimes sends a post in response. For some reason, only two streams can coexist. I would understand that if they ran off same IP addresses, but it’s not the case!

Were the limitations tightened or it’s also beyond the actual IP somehow?