Your two kittens are gorgeous! They both look healthy.
If the one has dental problems, it is the cause of her not wanting to eat the dry food and treats.
I brush my cats teeth, who is now 5 yrs old. She has not yet had to have a dental cleaning, but not all cats will let this be done. I also use a dental rinse and the toothpaste is from the vet.
One time her gums became inflamed at a younger age and she was put on antibiotics which cleared this up.
Your vet can help you with the gingivitis, there are even chewable cleaning disks available.
Good luck, and let us know updates.
Mona, Honeybun and Little Chloe