DOC-393 Updating note from Jira feedback

Author: forstisabella

src/connections/sources/catalog/libraries/website/javascript/upgrade-to-ajs2.md

@@ -50,7 +50,9 @@ If the source you intend to upgrade uses the in-domain instrumentation as well a
 
 ### Relying on Analytics.js Classic's `ajs_anonymous_id` cookie format  
 
-Analytics.js 2.0 removes inbuilt quotes from cookie values, resulting in a different format for the `ajs_anonymous_id` value when compared to Analytics.js Classic.  Though you can retrieve cookie values with [standard supported functions](/docs/connections/sources/catalog/libraries/website/javascript/identity/#retrieve-the-anonymous-id), you'll need to configure your environment to accept the new format using the `utility` [plugin](/docs/connections/sources/catalog/libraries/website/javascript/index/#example-plugins) if your implementation relies on accessing the cookie value directly. 
+Analytics.js 2.0 removes inbuilt quotes from cookie values, resulting in a different format for the `ajs_anonymous_id` value when compared to Analytics.js Classic.  Though you can retrieve cookie values with [standard supported functions](/docs/connections/sources/catalog/libraries/website/javascript/identity/#retrieve-the-anonymous-id), you'll need to configure your environment to accept the new format if your implementation relies on accessing the cookie value directly.
+
+If you have configured different sources for different subdomains of your website, ensure that you switch them to Analytics 2.0 at the same time - this will guarantee that subdomain tracking will not break. In cases when you need to gradually update to Analytics 2.0, the `utility` [plugin](/docs/connections/sources/catalog/libraries/website/javascript/index/#example-plugins) will help match the ajs_anonymous_id cookie format and ensure that users are consistently identified across your subdomains.
 
 ### Using a strict content security policy on the page