Have noticed over the past few weeks a strange problem with my tomatillos. They would look fine and then the next day they would have this strange white or yellow bumps all over the leaves. At first, I thought it was a grow light problem, so I moved the grow light farther away from the plant. Seemed to help but it was not a consistent solution. I also did a bit of online research when I saw this on my tomato plants, but I was using the wrong search terms. Once I saw it again on the plants, I search images for the same problem. It seems like it is Edema or oedema which is caused by too much water! So glad it is not a worst problem!
I am going to cut back on the watering. I also need to move this plant to a bigger pot, so there is more room for the water to spread and move away from the plant.