font size smaller

[mufc]

I use my own font on my sony ereader and in 'look and feel' my font size is set and always came out like I wanted but since I converted a bunch of books to mobi, now when I reconvert my epub books the font is smaller. I now have to go from small to medium font in sony reader to be able to read it. no settings were changed. I was using Calibre 8.45 all this time with no changes made. I upgraded today to 9.17 but it did not fix anything.
When I explode my book after conversion and look at the css the font size before was 1.08333em but the newer books are now 0.8125em
This is happening while I am still using the same conversion options as before.
Stumped

Base Font Size 13pt
Font Size Key 7.5, 9.0, 12.0, 13.0, 14.0, 16.0, 16.0, 16.0
Minimum Line Height 120%
Line Height 0.0pt
Tick “Remove spacing between paragraphs”
Indent size 1.5em
Text Justification Left Align