Within the same batch then the usual cause is using older cukes mixed in with fresher cukes. Older cukes are softer, more porous, and so absorb much more of the salt in the brine.

It is one of the main reasons using only fresh picked cukes is recommended.

Did you taste the brine before adding it? Sometimes if it is too salty going in you can add a smidge of sugar to the brine first.

Dave

I think you hit the nail (pickle?) on the head! We'd never made pickles before so we were a little overwhelmed by how quickly there seemed to be a million pickles to can! I mostly made relish out of the older ones, but some cute little ones did make it into our pickles. I'll be sure to schedule my canning more immediately this year. Thank you!