Comment by Galactic Navy Officer on Another World Territory Reform ~Starting Public Works with Earth Magic~ - Chapter 13.1

@Galactic Navy Officer Yeah, and it seems the older brothers were indeed from the mc's step mom which makes it strange that the OG mom died so early even though she had a restoration magic of some kind (idk if it's supposed to be a true healing magic or not),

But yeah, step mom award all the way!

@B P (Ult1m4) It's not just about having a restoration/healing magic -it's also about the magic's level and the user's strength. If the injury or illness is worse than what the power can handle, then the power can be overwhelmed. If the user is badly weakened, they can't use their power effectively. A weak or low-level user can be overwhelmed surprisingly quickly. There's also having the experience to know how to deal correctly with the problem, or even recognize it in time in the first place.

(There's an old D&D joke about who heals the healer.)

Over in the ElfQuest comics (most issues readable on their site), in the Shards war arc there's two healers. (Besides Winnowill, but she's the enemy and a bi***.) 

Leetah is much, much stronger than Mender, even though he was literally named for inheriting his healer grandfather's power. She also more experienced, being around 600 years old when he was born. When a human ally's hand is injured saving a member of the war party, Mender can only keep her from bleeding out or suffering permanent tendon damage; several days later, Leetah (who'd been off with the half of the tribe finding a safe place to live after the war) heals it fully in just a few minutes. 

(Why the weaker healer went with the war party is a long and spoiler-filled story.)

@Galactic Navy Officer That's interesting but not every isekai rules allow healing magic to heal illness though. Quite of few of them only allows Apothecary and Alchemy to heal illnesses while Healing Magic has different levels of restoration effects depending on the lore. I wouldn't be surprised if this manga had a similar lore. I'm having a hard time understanding which is which considering purification and clean exist.