change in file size is normal becuase different OS(like Windows, Mac, Unix) store 'new line' info differently.
some use CR, some use LF/CR, some use LF. more detailed explanation if avail at these 2 urls
http://en.wikipedia.org/wiki/Line_feed and
http://en.wikipedia.org/wiki/Ftp#Data_format
sounds like whoever uploaded those file have misconfigured ftp client..