My first guess is the yellow ones are muscovies (I have a 50% chance of being correct). Really, the faces on the darker ones look more like my runners when they were babies.
I am going to need to get some help to get the pictures of the feet. Your guess was the same as mine, but I was looking at the tails. the yellow ones have more tail and it spreads out more, and the mustard? colored ones have shorter tails. I have never seen an indian runner duckling, actually I have never seen an indian runner duck in person. I just liked the way they looked in pictures. My muscovies had black stripes as babies.
The ones with face coloring look kinda like my Fawn & White Runner ducklings (their coloring is that of their name). I don't have Muscovies so I do not know about that one.
the ones with the lighter beaks are muscovies! my friends duck hatch them about every 15 days seen tons of them. So your really light ducks with white looking beaks are muscovy.
Where did you order Muscovies from? most hatcheries don't sell them and most muscovy ducklings have the bean at the end of their bill i don't see that on yours.
if you'll go to this link you'll scroll down to post 9 you'll see what i'm talking about the bean on the tip of the Muscovy duckling bill. https://www.backyardchickens.com/t/659533/new-to-ducks#post_8906256