Are you using Firefox, perchance? It has a "bug" (not sure about that, but surely it's the only one that shows that behavior) relating to SVGs, so it used to size incorrectly the fouth icon. I worked it around some minutes ago and it should be fine.

The first icon should be Twitter, so maybe it's really Adblocker. I've tested it with uBlock Origin and it shows the same behavior but, honestly, I don't want to tamper with that.

In fact, the sharers that are provided are meant to be examples, and not part of the core library. I guess simply changing the name attribute of the sharer would end up in showing the button.