HI,
I have found the solution in the french Forum. You have to edit the item.php from your K2 template.
For Facebook, find <!-- Facebook Button --> (around line 289) and change :
js.src = "//connect.facebook.net/en_US/all.js#appId=177111755694317&xfbml=1";
for (exemple for french)
js.src = "//connect.facebook.net/fr_FR/all.js#appId=177111755694317&xfbml=1";
For Google +, find <!-- Google +1 Button --> around line 306 and change :
window.___gcfg = {lang: 'en'};for (exemple for french)
window.___gcfg = {lang: 'fr'};