You will need to recreate the bitmap font in general. In general, here are the settings I recommend for bitmap font creation in BMFont, important ones highlighted in yellow:
Font settings page:
Export options page:
Also, ensure you’re including the actual new line character in your bitmap font.
While those empty spaces above and below the characters may seem like extra, in many cases fonts use different spacing widths for different characters, and new lines are a separate character as well. If you don’t include the blank spaces you may be missing the newline character and the engine has to guess.