Light colored spots on this herb are caused by sucking insects. Possible culprits include spider mites, whiteflies, thrips, and leafhoppers. Most likely leafhoppers are the culprits. The insects have straw/needle-like mouthparts which they insert into the leaves and withdraw liquids and nutrients. This feeding activity results in coarse, white stippling. 

The herbs are fine to eat or dry in that they are harmless, but their potency could be affected, so they may not taste as strong as they would otherwise. You can remove the most damaged leaves. Usually, the plants push out enough new growth that is unaffected. Here is more on leafhoppers https://extension.umd.edu/hgic/topics/leafhoppers-flowers

Marian