jmkt on "[Plugin: WordPress SEO by Yoast] XML Parsing Error"

Hi,

My xml sitemap was showing fine and now I get this message. Does anyone know why?

XML Parsing Error: XML or text declaration not at start of entity
Location: http://www.lakescoaching.com/sitemap_index.xml
Line Number 2, Column 1:<?xml version="1.0" encoding="UTF-8"?><?xml-stylesheet type="text/xsl" href="//www.lakescoaching.com/main-sitemap.xsl"?>
^

Thanks

https://wordpress.org/plugins/wordpress-seo/