Breasts are different sizes after implants? Can fat grafting fix it?

You did not post photos, but fat can be used to help augment breasts. Fat does not increase the risk of capsule formation unless an infection occurs. Please discuss this with your surgeon.

I think you meant to say capsule?
If that’s the case then recurrent breast implant capsular station as an issue that can lead to implant failure.
Recurrent capsular contractions can be caused due to contamination with a very slow growing bacteria called staph epidermidis. The bacteria cannot be diagnosed or detected using cultures.
It cannot be eliminated while there is a foreign body in place.
If you have already have implants and have a symmetry then the best option is to adjust the implant size.
If you’ve had multiple capsular contractions than you are at risk for developing another capsular contraction and may eventually fail breast augmentation with implants.
Fat grafting is unlikely to increase the chance of developing capsular contraction.
I don’t see a good indication for doing fat grafting based on what you described. adjust the implant size on the nonproblematic breast to get symmetry match if needed.
Fat transfer with breast implants generally requires first removing the implants then grafting the breast followed by reinserting the same or new implants.
Grafting without first removing the implants puts patients at risk for implant damage with the fat grafting cannula.
I suggest you continue working with your current plastic surgeon or seek second opinion in person consultations with other local board-certified plastic surgeons in your community.
Best,
Mats Hagstrom MD