My client sent the print PDF I provided him with to a print studio. They replied that the black CMYK profile is set to 100/100/100/100 and they need it in 64/55/53/100. How do I fix that? I'm designing in Photoshop and exporting with Bleeds in Illustrator.
What the printer is telling you is that you're over-inking your rich blacks. Maximum ink coverage is almost always much less than 300% total (275% in this case), depending on the press and the paper, so a rich (or "built") black can't be 100% on all plates. There's more information on black vs. rich black here.
I'm guessing, since even RGB black from Photoshop isn't 100/100/100/100, that you've accidentally used the Registration black somewhere in the document. Registration black is only for registration marks, never for live art or text in a document.
To see exactly where you have problems, if the above hasn't made it obvious, open the PDF in Acrobat and under