Thank you for the photo - you have aphid on your plants. These soft bodied insects suck the juice from stems and leaves and can cause puckering and curling of foliage. They are easy to control. You can use your finger to squish them along the stems and new growth and also wash them off using a mild soap and water. Repeat every week for three weeks with a rinsing of water as aphid leave behind eggs. There are also insecticidal soap sprays made for houseplants sold at nurseries and home center stores. Just read the label to see if they work on aphid and also that the spray is made for indoor use. Keep growing, Marianne Binetti