“Warning: Cannot modify header information…”

I recently installed the plugin WP Since Last Visit. This involved making a few modifications to my index.php, header.php, comments.php, and sidebar.php.

With two exceptions, the thing works fine.

First exception:
The thing that’s baffling me is this error message:

Warning: Cannot modify header information - headers already sent by (output started at /hsphere/local/home/galen5/familywebwatch.com/blog/wp-content/themes/Blix/contact.php:7) in /hsphere/local/home/galen5/familywebwatch.com/blog/wp-last_visit.php on line 55

If I read the first sentence correctly, then line 7 of contact.php is: <?php get_header(); ?>. Line 55 of wp-last_visit.php is: );

This occurs when I go to a post’s page and click on one of the links in the top nav bar, like “Contact”. I’ve already been directed to https://codex.www.ads-software.com/Answers-Trouble_Shooting#Headers_already_sent, but nothing changed.

Does anyone know what’s going on?

Second exception:
I’ve successfully configured the code to show a “new” image next to a new post and when a new comment has been made on the front page.

But I’m having trouble getting the “new” image to show up next to the comment itself on the post page. All that shows is the “alt” attribute text next to the author’s name. I’ve told it where the image is the same way I’ve told the other functions.

Any ideas?

My site is: https://familywebwatch.com/blog_test/2005/04/04/another-new-post/

Sorry for the long post. Just trying to give you as much information as I can. Thanks for any and all help. ??