It looks more like sweet potato whitefly damage, to me, Carohit.

As marigolds are grown because of their strong smell and as a deterrent to many insect pests, I'd be very surprised if it attracted red spider. The definitive test is to look at the underside of the leaves with a magnifying glass and if the mites are there you will see them in their webs, often more yellow or even clear, rather than 'red'.

Looks more like thrips to me

thanks everyone for your feedback

Thanks, Andy. I should have thought of thrips--that fits the damage a little better, too.