I have always been very successful fixing bleeds using Vicki Welsh's method. She is a hand-dyer and quilter, and did a ton of research and experimenting to find the best, most reliable way of permanently fixing dye in fabric. If you search for "Save My Bleeding Quilt" you will find the pdf she generously wrote up for all quilters, free to use. Essentially she says use plenty of water, do not crowd the fabric, and it needs to be very hot 140°F, add a tablespoon of Dawn dish soap and let it soak overnight.
Having said that, I will say that there was one fabric I could NOT get "fixed". I processed it four times using Vicki's method and it was still bleeding. I finally figured out why - it was a saturated dark green DIGITAL print. The manufacturers of digital prints claim their fabrics are superior because the inks don't fade, they can print smaller batches, they can print on demand, blah blah blah. But ask them about bleeding, or runs (where the thread spins and shows the white backside, which looks like a run) and suddenly they don't know what you're talking about, they've never heard of such issues. I've about had it. I'm so fed up with these crappy digital prints, I'm happy to go back to my fat stash of conventionally printed fabrics and use them instead.