The answer is probably: Yes.
I had this severe brown staining problem with Tetenal blix. Kodak blix gives perfect whites regardless of blixing time (within specs of course). In the meantime, you can reduce the problem by blixing only 30 seconds or so to reduce staining, but then there is probably much residual silver and halides left, but you can reblix them with proper stuff when you get it.
I also used bleach made of potassium ferricyanide and sodium bromide and E6 fix (as two separate stages, wash in-between) in troubleshooting before getting proper Kodak RA-4 kit, and they worked very well.
I really can't stop wondering why they make this kind of kits. There is really no reason to premix these two solutions at factory. It's like sabotage towards traditional photography.