How can I tone my lower abs?

I’m already thin. I’m 5’3 and weigh about 115 lbs. My abs seem pretty toned but the lower abs seem to have a bit of fat that keeps it from looking as toned as my upper abs. How do I make it look toned? I can’t lose any more weight because I don’t want to be skinnier!

I do leg lifts, v-ups, butterfly kicks, and all that.