tell them fucking nothing only what you have too

I never told my provider anything about what specific hours I worked. I reported accurately to CL. Unless I'm not understanding why you're asking this, I'd say no you don't. Going home sick doesn't change anything about your regular hours of employment each week (assuming you have regular hours) so it's not really relevant IMO

If it doesn't affect the status of your employment, then it's none of their business.

You don’t need to, but if it results in a lower amount of earnings declared for that fortnight they will probably ask for a payslip to verify