Certified GKH Gardening Expert
Yes this does sound like it is getting bound in its pot. But from my experience, there is another culprit that will devastate the plant as well. Spider mites will be a continual battle, but if you know what to you it will be easy to control.
Let's address your first issue. The best way to replenish its health will be re-potting it. Get a pot that is 1 or 2 inches deeper than the one it is in, and break apart the root ball carefully so you can get the old soil out. Place enough dirt in the bottom of the new pot to bring the plant to where it needs to be when you fill in the dirt. Fill it the rest of the way, shaking in between to get all of the soil settled. Then water in for its first time. You may have to add more soil after you water.
As for spidermites... Here is link to some organic pest control methods: https://www.gardeningknowhow.com/special/organic/natural-home-pesticides-organic-garden-pest-control.htm