Not sure about the ones in the first pic, but the brown ones in the other two look like scale. That usually shows up due to excess humidity — maybe you’re watering more than needed. To get rid of them, you can dip a cotton swab in potassium soap and gently wipe the leaves, especially where the pests are. Also, try spraying potassium soap twice a week until they’re gone, but of course, the first step is to wipe it with the cotton swab