Sorry but I am getting confused by some of the posts about Daggers on here.

Do all of the One Handed perks affect Daggers?
Or is it just the enchantment 'Fortify One-Handed' that doesn't affect Daggers?

'Fortify One-Handed' doesn't effect daggers?

I think perks (if you mean Armsman) affect Dagger damage - easy way to check is to make a save game, look up your dagger's damage in inventory then put a perk point in Armsman and recheck the damage. But Fortify One-Handed enchant definitely doesn't affect daggers.

The only rational thing would be: Yes, they are affected.