Didn't notice but at 3 months old and you havent already transplanted your plant you need too.And the hieght at only 18 inches in 3 months sounds like you have it in a small container.It needs a bigger container for root growth.I'd recomend you transplant it.Use a 3 to 5 gallon container.Get new soil too fox farm's is the type of soil i use.And if you havent feed it give it some nutes.You can find fertilizers at your local nursery along with soil you need.Good luck and i hope this helps you out.Happy hunting! Oh yea those wilting and yellowing leaves dont worry about them its a natural process this late in the plants life!