PDFs suddenly saving 4-5 times larger

I do a monthly newsletter, very similar format and procedure every month. Using “High Quality Print” preset, my documents have always produced a PDF between 3.7 and 3.9MB in size. Suddenly, using same # of pages, roughly same # of photos, “saved as” layout reused month after month, the document is creating a 17-25MB PDF. 

Even more interesting, when I open old InDesign newsletters that originally created a 3.7MB PDF, and without changing anything turn them into a new PDF, they are now 5X bigger. (See screenshots - I made absolutely no changes to this layout, just opened it a few months later and saved it to a new PDF that turns out to be 5x bigger) Did something happen with InDesign 26 (which I did not voluntarily switch to?)