Hi i think i can help you out
the steps are
1. fist download the plugin called regenerate thumbnail, install it and activate it.
2. Goto Woo-commerce>>Setting>>catalog. in it set the thumbnail size like i do it to 550 X 550 you can choose whatever you want . Click save.
3. Goto Media select all the items .In the Bulk actions drop-down select regenerate thumbnail. your thumbnail will be regenerated
now clear your cache and visit site ?? DONE.
you can visit my website (under development) crazycollections
