Cooper Discoverer at3

3 years ago I fitted Cooper Discoverer AT3 I have done about 25000km on them. I accidentally curbed one of the rear tyres while inspecting the damage I noticed hairline cracks on the side wall checked the other 3 tyres and all have cracks. I have tried to contact them via email and on Facebook

You don't expect this type of damage from top shelf tures I've googled this and it seems to be a bad batch of tyres