Certified GKH Gardening Expert
This sounds like a case of scale bugs. This is very common on all citrus. You can scrape off what you can, and then spray neem oil, or any insecticide that suites you. Scale will cause these symptoms and more, so it is best to get them taken care of as soon as possible. Just don't spray neem oil in direct sunlight. This can cause burning to the leaves.
Here is a link to some article that will give you more information on making your own pest control, among other things: https://www.gardeningknowhow.com/special/organic/