Certified GKH Gardening Expert
Unfortunately, your photos did not come through. I am unable to see the plant to get an idea of what is going on.
Usually, it will boil down to 3 factors- Soil nutrient content, temperature, and light amount.
These plants require warm temperatures and quite a bit of feeding during the growing season. They will require full sun, as well. This will mean that using a window to light them will give very slow results.
For a refresher on the plants' care, read this article: