Revisions not displayed on Home Page

My “Page Revisions” option under edit page has disappeared from wordpress. This only occurs on my main page CapeK9Cardio. I found this out when I made a mistake on the page during editing. After saving the page I could not go back to another version. I had to download a cached version from Google!

Any idea how this could have happened or how to fix it please advise!

When I go to edit the page here is my error code:
Fatal error: Allowed memory size of 33554432 bytes exhausted (tried to allocate 33969 bytes) in /home1/capeknin/public_html/capek9cardio/wp-includes/theme.php on line 180