Formatted text all over the place

I know this is an old plugin, but it’s the best I have come across. However I am having a weird issue that I don’t now how to fix. I have the following line to show as code:

<p>This is the first page I’ve created!</p>

But the issues that come up are:

“This is” – displayed as bold
“the first” – displayed in green
“page I'” – displayed in black text
“ve” – displayed in green
“created” – displayed in blue
“!” – displayed in green

I would expect the whole of the text in the paragraph tags to have all the same formatting.

How do I change this?

TIA