I am seeing the same issue with the white space on my end also. It looks like this could be an issue within the code of the product pages, so the way to resolve this depends on the theme that you're using.
If you are using one of our free Shopify themes, our team may be able to help you remove this white space, but do note that there are limitations here if you have done a lot of custom coding on your theme, or if a third party app is causing this - in which case you would need to go directly to the app developer.
If you're using a third party theme, then you will either have to go to your theme developer to try and resolve this, or if they cannot assist here you could also look into this with Shopify Experts. Experts are freelancers that charge their rates based on the work that they do, and they're equipped to help out with custom code or other theme issues.
On another note, since you provided the link to your store I was able to have a look around - you have done a great job with everything! Love the structure of the homepage, very easy to navigate overall. Are you looking ahead to this year's BFCM period? Putting aside the issue with the white space, once that is resolved I can see that your site is ready to take on this season! In preparation, you can take a look at our Shopify Blog article that has some great tips to get ready with the 2021 BFCM Checklist.
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