Yes, I'd contact them one by one. The best time to raise money is when you don't need it. And most investor relationships take awhile to ripen, so to speak, so if you start nurturing those relationships now, then you'll be in a good place with the investors when fundraising becomes a priority.

It can't hurt to reach out along these lines: "Thanks so much for your interest! Were you just checking everything out? What do you think? Let's schedule a time for me to walk you through the current iteration of the product. How about next Tuesday at 9am EST?"

I guess what I'm saying is that why these investors signed up really doesn't matter. You need to build your investor pipeline regardless. And they're making it easy for you!

Hope this helps,
Austin