How to change header text style (e.g. header) without changing all surrounding text?

[Craig Kelso]

Hi all,
I'm finding an issue where I change the text style on a piece of selected text (e.g. from 'normal text' to 'heading 2')  and it not only changes that text style of that selected piece of text, but also changes the text style of text I haven't selected both above and below this piece of selected text.

Steps to replicate:
1. Select string of text with cursor.
2. Select text style editor drop-down list.  Choose 'heading 2'.

Expected result: only the text I have selected changes to 'heading 2'.

Actual result:  the text I have selected changes to 'heading 2' AND text I haven't selected both above and below this selected text also changes to 'heading 2'.  The end result is that I have a whole paragraph above and above my heading also looking like 'heading 2'.

** any suggestions on how to fix this issue would be very much welcomed :) **

[Terry Cromwell]

In addition to the above advise "need to have line breaks on either end i" I noted that if the there is no text on the lines above and below the selected text, this also causes the Header change to be applied beyond the selected area.
=================
Ex In this example, if I highlight "My Header Text" and change it to Header 1, the "Text in the next Paragraph" will also change to Header 1.
.........................................

[NewLine]
My Header Text
[NewLine]

Text in the next Paragraph below....
=================
Ex In this example, if I highlight ""My Header Text" and change it to Header 1, one the selected text. "My Header Text" 
.........................................

Some Text[NewLine]
My Header Text
[NewLine]Some Text 

Text in the next Paragraph below....

[Brant Schroeder]

@Craig Kelso This is very common issue in any online editor.  If you want to have a header it will need to have line breaks on either end in order to only change it.  

This will work.

This is a paragraph above the header.

Header

This is a paragraph below the header.

This will not work because it will apply the header style to the whole line and not the selected text.

This is a paragraph above the header. Header This is a paragraph below the header.

[Craig Kelso]

@Brant Schroeder  thanks so much, I've done this and it was worked.  cheers