Part of being a good DM is knowing when to pull your punches. Granted another part is to know when not to; however that said, out of game tutoring or pointers are usually the other way players get better (since in game they don't see the stats of enemies, despite that they can at least observe their tactics.

I would point out, sometime between games, that they CAN in fact find potion shops or magic shops in towns. Perhaps they thought they didn't exist. You said it was a low magic game after all. Did you ever say that there were healing shops in town?

As for HP per PC, those are low Hit Die classes for the majority. If you are overly concerned, I've always been pro-max HP per level, with enemies getting listed to 75% hp per HD for random encounters and bosses having Max HP themselves. (However boss fights are always at the disadvantage for turn economy with my DM'ing)

I'm curious about this Warrior class... how custom is it vs how much like the Warrior NPC class is it? Because PCs should not be playing NPC classes. (A Warrior gets d8 HD and no feats, so it's worse than a Fighter)