There's a couple places I'd start with troubleshooting this. First, make sure that on your wired network, you can get the advertised 100mbit. It's not unheard of that a consumer gateway/router device is unable to sustain 100mbit, especially if it's more than a few years old.
What kind of clients are you testing this on? And how do you have the AP's configured channelization wise? Are you using 80MHz channels? Furthermore, do you see your clients on 2.4GHz or 5GHz?
It's unlikely that clients on 2.4GHz with 1 stream (or even 2 stream) can saturate 100mbit. Reaching these speeds will more or less necessitate that the clients are associated on 5GHz.