Custom CSS to change colour affecting spacing?!

Hi there,

I added some custom CSS so I could change the colour of my headings.

It seems that this code has also created weird spacing when viewing my site on my MacBook? I have attached a screenshot.

When I duplicate the page and take the code out, the ugly spacing disappears, even though the font size was the same?

Any ideas how I can customise my headings so they're green without affecting the entire site heading colour?

This was my code:

body h6, .sqs-layout .sqs-block.html-block h6, .sqs-layout .sqs-block.markdown-block h6 {
   color: #2a9837 !important;
   font-size:40px;
   line-height:46px;
   font-family: Calluna, serif;
   font-weight:400;
   text-transform:capitalize;
   letter-spacing:0px;
   }

Thanks!

@RumJungle123 You should shaer url to check