So I fancied a change and decided to change my looks from daedric armour. After rummaging about I come across a full set of blades armour so decided to improve and enchant but when I went to improve them I could only make them flawless the same happened to mehrunes razor. My smithing is 100 and normally I make stuff legendary is it just because the armour is steel?

blades is improved by the steel smithing perk.
mehrunes razor is improved by the ebony snithing perk.

according to the wiki blades armor isnt governed by any perk bonus so it stays at flawless, but can be improved more by enchants, or potions