Is it normal to have one expander softer than the other after fill completion?

Two possibilities come to mind. The first and most common is that there is nothing wrong, one breast feels more firm and they will feel the same after implants are placed.The other is that you might be losing some fluid from the softer expander side, especially if there is a noticeable change in a short time period.You should voice your concerns to your surgeon and let him examine your breasts prior to undergoing exchange, in my opinion.

Hopefully if you are scheduled for surgery next week then your surgeon has seen you recently to chose your definitive implants and discuss specific plans for your surgery.  If so, I'm sure that if there was anything wrong they would have let you know.Often there is a difference between the expanded breasts.  Generally this will resolve with the implant changeover procedure.  The "pocket" where the implant is placed is commonly slightly different, as is the tissues over and the capsule that forms around the implant - so it is common for one breast to feel softer than the other.If you still have concerns prior to your surgery please contact your surgeon to make sure that your expectations are met and worries resolved before your operation.All the best,Dean 

Unfortunately without seeing pictures this can be a very difficult question to answer.  However tissue expanders hardly ever look good and/or feel good.  They have a job to do which makes him very hard and tight.  Depending on what part of the breast was removed from each side it can have some significant asymmetries from left to right.  This can hopefully be corrected at stage II with your implant insertion.