On both arugula and romain in garden.
That looks a lot like leafhopper damage. They come in many shapes, colors, and sizes. I would use an insecticide like azadirachtin. This is an extract from neem oil, and is my go-to.
https://www.gardeningknowhow.com/plant-problems/pests/insects/leafhopper-control.htm
https://www.gardeningknowhow.com/plant-problems/pests/pesticides/azadirachtin-vs-neem-oil.htm