I don’t think there’s Silicon around the cover but it’s not caused any problems for 8 years so I’d have thought it unlikely that it would start now. But definitely another thing to rule out.....
I'd at this stage carefully rake out the stained area and hairline cracked areas... Re-grout in a good flexi grout.. Fingers crossed .. May be the ticket.. Worth a try!...but most certainly cracks due to movement/ delamination and staining more than likely from behind ( Impo)...