Start with Why
Sounds like you are building or already have a relationship started with the owner, I would say keep doing that, see if you can with the new engineers as well. I agree with the other comments, you should simply offer a change order due to the time difference and simply be upfront with it that you are not trying to take advantage of anything, but simply business expenses are not they same as they were 6 years ago. I think most business folks can empathize. For the ones that may be trying to make there mark of importance to their company, I think you simply "negotiate" the change order for their ego, and they will feel like they have won as well. Good luck, sending best wishes for you as I understand these are uneasy moments.
Sounds like you are building or already have a relationship started with the owner, I would say keep doing that, see if you can with the new engineers as well. I agree with the other comments, you should simply offer a change order due to the time difference and simply be upfront with it that you are not trying to take advantage of anything, but simply business expenses are not they same as they were 6 years ago. I think most business folks can empathize. For the ones that may be trying to make there mark of importance to their company, I think you simply "negotiate" the change order for their ego, and they will feel like they have won as well. Good luck, sending best wishes for you as I understand these are uneasy moments.