vlc on "Not all strings in contact form can be translated"

I have a multi-lingual installation of ZP 1.4.12 and the "contact_form" plugin activated. While the multi-lingual setting allows me to translate most of the text elements in the contact form, the actual form fields (Name, E-Mail, Phone, Enter CAPTCHA, Subject, ...) maintain their English text (in German as well as in Spanish translation).

Is there a way to also translate these elements?