Those are great options for your 401K -- I'm at TIAA CREF and I'm a bit jealous.
I'd start by figuring out the allocation you want. Here's what you are currently doing:
78% US Stock
16% INT Stock
6% REIT
If that's what you want to do, fine. There isn't one right answer. My personal asset allocation (as a 38 year old married homeowner) is:
54% US Stock
26% INT Stock
10% Bonds (2% INT)
8% REIT
2% Other (peer to peer, specialty funds)
That's according to Personal Capital. I'm planning to up my INT % of both stocks and bonds with next years IRA contributions. I also own a house, which makes me less concerned with the REIT.
So first figure out the allocation you want, and then figure out how to hit your new allocation with the options at hand while minimizing the fees. For example, if you decided you wanted:
60% US Stock
25% INT Stock
10% US Bond
5% REIT
You could adjust your 401K accordingly, increasing your American Fund, adding VBTIX, and (slightly) decreasing your REIT.
In all honesty, though, at this stage of early investing, I'd probably just focus on minimizing fees. For example, I might just put my whole 401K in the 500 index (keep the small and mid, too, if you want, and maybe add a bit of VBTIX) and plan to do my REIT / INT Stock exposure in my IRA.