spacing on pages

Hello

I created several pages using the blackbird theme. Certain pages that I have created page wont allow me to put spaces between lines. and it wont allow me to separate paragraphs and the whole page is all together in one big paragraph. How can I put spaces or separate paragraphs on these pages? When editing the pages I hit enter to create the spacing but as soon as I click update it just compresses everything bac together in one big paragraph.