Mealybugs, mites, thrips, aphids, spider mites(pretty much only spider mites if you can see webs on the inside of the leaves, use a magnifying glass), scale bugs (only if you see little goo like boogers forming on the leaves or stem, then they will grow hard shells to protect themselves.
If you think they are bugs do this, go to you local gas station buy a pack of cigarettes boil 3-4 (depending on plant size) in water for 5-10 minutes. After let the water cool (WEAR GLOVES THE NICOTINE WILL GO RIGHT THROUGH YOUR SKIN), then lightly spray the leaves with it everyday until you see a difference. (the nicotine and other chemicals will kill these things, unless they are scale bugs that have scales formed around them)
Remember you are using chemicals that are VERY transdermal. If you get it on your hands wash them with water and soap as quickly as possible, you wont die, but you might feel dizzy.
This is a natural bug remedy, it works almost every time and it is very cheap.
(it is easier and safer to actually soak the cigarettes or cigars in water for a few days) both methods are effective, the soaking is more effective)
(and trust me you wont hurt your plants, this is one of the oldest tricks in the book, been around since 1800's)