Throw in some Book of Iron Might (Malhavoc)?
Problems I'm seeing:
There's no cleric.
You're nerfing items. There is no good fix for this in 3rd Edition. There's some "low-magic rules" that you can probably find in Unearthed Arcana, but they're not good.
Items give a fighter bigger bonuses than they give non-spellcasters. On the other hands, fighters are very heavily item-dependent. A wizard missing a Headband of Intellect is missing a few bonus spells, and more crucially, 3 points off of save DC. A fighter needs that Strength-boosting item and a magic weapon for offensive purpose. (Note that rogues are also affected by this; it's hard to pull of a sneak attack if you can't hit, and you want your Gloves of Dexterity and magic short sword to ensure this... with your lower BAB.)
For defenses, a fighter needs magic armor, maybe a magic shield, a ring of protection, maybe an amulet of natural armor, and more options as they gain levels, just to make up for AC never improving. For defenses, a wizard needs to be able to cast Mirror Image, and have a backup in case what he's facing has true seeing or something.
What surprises me is that the fighter's hurting the most. The ranger is a pretty weak class in 3rd Edition, and the rogue, while not being as weak, has fragility issues that should be affecting it even more than the fighter (especially without items).
Other than the rogue, none of these PCs get social skills as class skills. I'm not sure why the fighter is doing worse than the other PCs.
firstly- we would use more books if we had them. But I should address that the world uses rather low magic rules but we make our own. Healing magic is a lost art, and most of the healing is from potions (their cheaper then in the book obviously as thats one of the only accelerated healing agents) Also we really just say "if your character's backstory would allow it as a class skill, it is. The fighter and the wizard both have diplomacy since one grew up dreaming of knightkood and learning how to be chivalrous, and the other is a teacher at the last school of the arcane.
as for 'needing' magic armor and weapons, thats not exactly true. we use the 3.5 system basics, but not much else other then it's skeleton. magic items are only 'needed' should some mythical monstrosity with double their CR show up, and thats an end dungeon encounter normally. you can get your armor enhanced up to +6 or 'flawless' grade(still non magic) in our tables, with any blacksmith good enough, and same for weapons. anything higher then that calls for some kind of master craftsman.
Because it's low magic that means low magic users for both the players and the enemies, usually saves are less an issue then health. It's much more 'realistic' in a sense but thats not really the correct term I think. very little magic is used or shown, and the only reason we have the wizard is because one person came up with a fantastic storyline with him. so we're not nerfing items, we're not including them at all because they usually unbalance our games. (we metagame too usually in higher magic campaigns)
Defensively the fighters pretty fine, +4 plate armor, +3 shield, 6 dex, and his fighting talent (burning a feat to permanently gain prowess in a fighting style, something we also do differently) giving him an additional +2, giving him a normal 23 AC. he only gets HIT half the time because I roll the enemy good or it's a melee enemy as good as he is. His lacking is in how little he ever gets to do recently. Their in a city of people mostly trained in archery and beast taming (so lots of rangers and animals) and since he purposefully takes the aggro on the animals, he's singled out while the others pick off the ranged users, only problem with this is how many he keeps taking on at a time (5 tigers was the last encounter he took on, if he hadn't had the ranger hidden away pecking at them he'd have died)
when I ask something I can give him I really don't mean something out of the book, that won't really do much other then the basic things that he can get in town non-magically (spent a week studing a subject, +1 int ect) and something like extra speed doesn't really help when most enemies aren't any faster then he is or aren't by much. defensive spells aren't really an option as his character won't accept them (self imposed honor code, his character is supposed to kind foolish like that) and most spells that aren't "I point the deathball in that direction and hope it doesn't hurt me too" have a 30-40% chance of just not working due to how hard it is to use and the wizard doesn't know them well since he specialized in fire and ice magic. (walls of fire do help sometimes though)
I'm out of ideas as to a creative method of making him able to do better against large numbers or rangers or both even, thus my posting here.