Make sure you have Formidable styling enabled in both the Formidable -> Settings and the individual form settings.
Compare the form preview page with the form in your theme. Any differences are caused by your theme.
Several themes are adding extra space between field labels, the required symbol, and fields. WordPress adds HTML (<p> and <br/>) automatically, and some themes send it through this WP filter multiple times which adds paragraphs and line breaks inside the form. In many of these themes, you can fix this by replacing [formidable id=x] with
[formidable id=x minimize=1]. This will minimize the form HTML so there is nowhere for your theme/other plugins to add the extra <p> and <br/> tags.
Formidable is 1) very well-thought-out to be easy enough to use while providing sufficient breathing space to customise and add deeper coding and 2) its stand-out feature is the quality, care and consideration taken with forum advice. Pretty much every single entry on this forum gives some useful information and is politely given. I have purchased a number of premium plugins and the support varies wildly; this is the best money I've forked out.
Formidable is perhaps the single most useful WP plugin I've ever come across - wonderful product and I must also say extremely fast support response.