Nah, you're a solid level for it, as long as you have been buying upgraded weapons.
The red slimes hit hard if you use fire on them, but fire does a lot of damage... try and save that for a final blow!
Try inflicting Bleed or Stun on them with your Sigil Abilities too! Pure damage isn't always the way.
Otherwise, make sure to watch your HP, and heal up as you need. Don't forget about the Strip ability. Having a good stock of healing items will help too... and there's a semi-hidden one in the room just before the Underworld if you look carefully.
Hope all this helps.