That is a known issue that occurs in Adobe Reader when scaling your artwork to fit your device's screen.
At times, lower case 'L's and capital "I"'s appear bolder than they should on the PDF proof.
Something like this:
If you zoom into the text, the bold "I"'s and "L"'s will appear much like the rest of the text.
See below how the L's in 'all' ad 'family' look better once zoomed in.
This issue is not a problem with your artwork and will not be printed with the overly bold L's and I's on your finished product.