Blank Page Need Help 1.3.9h

Need help! When I add something to cart the page goes blank. Notice following error in log.

PHP Warning: Cannot modify header information - headers already sent by (output started at /home/content/27/7149227/html/includes/languages/english/a_pink_boutique/header.php:2) in /home/content/27/7149227/html/includes/init_includes/init_templates.php on line 78

Is this my problem.

Try switching to the classic template
If that works then it is something in your custom template

I switched to classic and it worked fine. How do I find out what is wrong with my template. Thanks

Confine looking at files in folders named "a_pink_boutique"
Start with /includes/languages/english/a_pink_boutique/header.php on line #2

https://www.zen-cart.com/tutorials/index.php?article=82

Thanks Kobra for the info I will research that for the future. I reloaded the pink boutique and it is now working fine.