Cracks on tire - still safe to ride? I just experienced some uncommon cracks on the tires (Schwalbe Durano Plus)

The tires are pretty new (less than half year old, and used max. 1500 km).

I inflated 6 bars in the tire, and according to the specs 6-8 bars should be normal.
Is it possible that this cracks are caused by overinflation? 
Should I immediately replace them or is it still safe to ride like this?
The type of tire cracking that is most worrisome is when it's accompanied by bulging areas from the tube pressure. This implies damage to the casing, which in turn implies a tire that might very realistically fail at any time. The casing is the major structural part of the tire, not the rubber.

Cracks in the rubber like this look bad but almost never result in any issues themselves. When they do, usually its actually something along the times of the casing getting damaged in some kind of incident or condition that also caused the rubber cracking.

There's some distant hypothetical risk that the crack makes the casing more vulnerable in that spot or causes some kind of stress riser, but basically it's fine.