Be thankful you didn't rely on Devlan Miracle... err.. Devlan mud.
washes currently seem to not have the pigment of their previous washes. Not sure if that was intentional or not, and I have no experience with either sepia so I can't really comment. You may have gotten a bad batch, or the pigment settled... any number of issues could arise.
I'd check out other ranges for options. P3 makes some nice inks, and there's Vallejo's monstrous range to choose from. Secret Weapon has an entire section of washes that many people swear by, and actual examples of the wash after use on models! (customer support is awesome for them too)
So you have options, just need to explore em.
Good luck, but understand you -may- have to take some of your models as a shade or two off what the rest of your army is. I'm having to do it with my Nids atm
... sucks but you learn to work with it. And honestly, having some variety for Nids or Ogres would be all that noticeable; even animals in the wild come in a whole mash of shades and shadows.