RSS Feed Error

My RSS feed https://craftcore.ca/feed has an error:

XML Parsing Error: XML or text declaration not at start of entity
Location: https://craftcore.ca/feed/
Line Number 6, Column 1:<?xml version="1.0" encoding="UTF-8"?>
^

I used feed validator on my site and it shows that there are blank spaces before my RSS code:

https://feedvalidator.org/check.cgi?url=http%3A%2F%2Fcraftcore.ca%2Ffeed%2F

Previously, I used the “Fix Rss Feeds” plugin, which worked for some time, but now the error is back even though the plugin is still active.

Anyone have any advice for me? Thanks!