Nested IF statement returning false, only on some cells. yet formula is the same

My formula is the same for all the cells yet some follow my IF formula while others return FALSE.

It returns the false on a few, not all, of the "Yes" responses

Formula: =IF(ISBLANK(B9),(IF(ISBLANK(C9),(IF(ISBLANK(D9),"No","Yes")))))

I have tried both copy/paste formula and manually typing the formula in the incorrect cells. Both return "FALSE"

Thanks in advance.