I think it can be challenging to grow many ground cover plants with low light. They usually are more shaded than the rest of the plants, and some of them will start growing taller to get up to the light if the lighting isn't high enough for them so they turn out not being ground cover anymore. For some good low light foreground plants to use instead you could try a bunch of smaller crypts, they should grow fine in that lower light and won't get tall although they will be slow growing.