how are those buttons getting added? That is an abnormal place for the buttons… and wondering if you have the wp share this plugin running and if its doing that?
if you are using the WP plugin, you need to make sure that they do not auto add their buttons to the page content… they wont work since they dont grab the canonical url…
instead, you should be using the SP Share This plugi… and we provide our own template tags for you to add to your sp theme to display the buttons where you want… I assume since you said you are changing the button size, you are doing this in the sp plugin… but its not changing because those are not our buttons…
as mentioned, you need to add template tags to display the buttons where you want…
see: http://codex.simple-press.com/codex/plugins/our-plugins/available-plugins/plugin-share-this/
for the tags and some suggested locations for them…
Now, if you dont have the wp plugin share this installed, please show a screenshot of your share this options in the sp plugin and tell us where you put the template tags for display…