Indented corner of lip from lip fillers, fillers have not been able to fix it, what can be causing this? (Photos)

Ive been getting my lips done since 2020 and never had any issues. However i noticed a dip/dent forming by the corner of my lip. I dont know what caused this but even filler hasn’t been able to fix it. I got more filler to even my lip but after the healing period the dip reappeared. It also is a completely different color than the rest of my lips. You can notice it a lot and its made me even more insecure about my lips.