I'd like to know what type of lawnmower you're using and when it was last sharpened or had a new blade - they look like 'chewed' ends rather than cut, which become more noticeable as the grass grows again. Is it possible whatever you're using is blunt?

The other possibility, especially if your lawnmower is blunt and you've not fed or maintained the lawn other than cut it, is red thread disease, but I'm not seeing any red or pink threads, even with magnification, and the weather's not exactly been very wet in the last month or so. Well, not here anyway, maybe it has been with you.

Yes, they look much more like shredded leaf-ends, than seed heads, to me. Sounds like a slow rotary mower with very blunt blades. Possibly also a tough species of grass, such as tall fescue.