Increasing Milk Supply

A teaspoon of Brewers yeast in my daily smoothy does the trick for me. Enough so I had to cut back on my daily consumption! Mixed frozen blue berries, natural unsweetened yohgurt, 1 banana, Tablespoon of LSA mix (ground Linseed,sunflower seed & Almond)and vanilla flavoured soy milk.   

Brewers yeast is good... also nuts and oats and bananas.
Will say too though that your supply may not be dropping at all, your body gets more efficient at making the milk and unlike when they are newborns and it is stored before needed it is "made" as it is needed when they get older.

Yea I just assumed that it's been dropping off as she now sleeps through the whole night & when I wake up my boobs no longer ache like they use to if I went without feeding for so long

What Bizzy said, your supply will be sorting it's self out. If you're worried pop her on the boob more during the day. I've got the milk flow here & yep it works.