Thank you for the question.
I believe the most important thing to do here would be for you to speak to your PS to see following instructions, I am sure that a revision would have to be done and replace the implant which is deflated, these have a warranty in some cases, so check with your PS for the records.
Go to a plastic surgeon who will deflate the other under local anesthesia. Then after you finish nursing, have them removed and replaced.
You need to see your surgeon for deflation
You can have your surgeon to deflate and suck the saline out under local anesthesia in office. You can have them removed and replaced later.
If you have one ruptured SALINE implant and want to even out the sizes while you are still breast feeding, you can visit your board certified plastic surgeon and have them deflate the intact implant. That can easily be accomplished under local anesthesia by numbing the skin and inserting a needle and "popping" the intact implant. The saline can be removed from the implant causing a controlled leak. This should allow the breast to even out in size since both implants will be deflated. Then, when you are done breast feeding, you can return for implant exchange and replace with either the same implants or replace with Silicone or other style.
A visit with your local board certified plastic surgeon is the right thing to do. Replacement with some capsule work is the procedure he or she is likely to recommend. Good Luck!