You'll have to go to their page to see the injury before you know what you need to treat them.

A green potion would heal a broken paw

A yellow potion heals a broken tail

A red potion heals the infected wound

If your wolves have a red cross it means that have one of the three possible injuries. This can be cured by a Red, Yellow, Or Green Healing Potion. Make sure you know the injury before buying one of the potions because each heals a different injury. Or if you rather not have to match the injuries you can use a Robin Feather to heal any of the three injuries :)

Hope this helped! I might not be the best at explaining it though I bet more will post answers to your question.

(P.S. In your case, both of the wolves have Infected Wounds so you will need to use 2 Red Healing Potions)

(P.P.S You can find these potions and feathers in Barter or craft them with certain relics)

Edit: Oops sorry. Pretty much what they said ^