I'm using a single NodeJS/Express server to dynamically generate marketing websites for my company's brand partners. In short, visitor hits one of these sites, I fetch some basic info from the database that corresponds with the URL they hit, then render a template server-side that gets sent to the requesting visitor. Visiting something like "www.FlyFoo.com" would generate different pricing and some different copy from "www.FlyBar.com", etc. according to the specific products/plans offered by that partner (served from the same server though). Most of the images, site layout, variable amounts of copy, etc will be the same. This data fetch and render is not done async, rather before the server actually responds to the initial request for the page.
Are we shooting ourselves in the foot here with SEO? Should I be architecting this with subdomains instead, then pointing domains like "www.FlyBar.com" to something like "flybar.baz.com". The decision to use separate domains was not mine, but I need some technical reasons to justify going back to the table and arguing for a different approach.
Note: I am developer/designer, but I have very little experience with SEO