Which plugin causes 500 error

Hi

I’m trying to work out which plugin is causing the 500 error on my website.

Three times in the last few days my website has a 500 Internal Server Error which my provider support tells me is because the .htaccess is being rewritten wrongly by a plugin.

They have told me to work out which one but I have no idea how to.

Any help would be grand. I’m not very well-versed in code so please keep it simple.

Here’s my website http://www.whodunnknit.com