No, avast isn’t the only one and the number of tools doing so is growing (as they say) each day.
There are already many others that also block a entire IP if there is malicious activity on it and especially if there is a lot of it going on.

Use the link I gave you, if you haven’t done so already and avast will have a look.
If nothing malicious is found they will allow your domain.
Keep in mind that it is weekend so it can take a bit of time before they have a look.