Contact sheets in PDF output size extremely large

I generated several PDFS in the same way as I did all others and suddenly it generated one that is 21 mb while all others were around 250mb. Now trying to generate it for another project, and its 300mb so I went back to this other project that generated the 21mb file and tried again with same settinngs and it cant replicate that result of a 21mb file. I used to always get manageable sizes of contact sheets, any ideas anyone?  😞