Different IPs get blacklisted for a reason, as mentioned earlier, it could have been something like the SMF database have seen your IP been put on the blacklist somewhere else, and it moved on here since we use SMF.
Some internet providers give out the same ips on different instances, for example, if you are at a college network, they sometimes have 1 single IP for a wider area in the college that more than 1 person use. Some towns or houses use the same connections at times, depending on the internet provider.