Sudden PHP Memory Leak in Codeigniter
OK so I figure it out, here is what I did and what was happening.
1) First I had to get xDebug installed. (https://xdebug.org/wizard.php)
2) Then I could see the errors when trying to load the page.
I had reached an maximum allowed nesting limit in Codeigniter. This was due to loading models within models and back again. I didn't realise cross model usage was not allowed.
So I moved my class based construct loading of primary models to the autoload.php file.
This got things loading again.