Agile places a high value communication, especially face to face communication. You can pick up things face to face that you can't in an email.
And yet, somehow, projects like, oh, the Linux kernel, the Apache HTTPD server, and just about every other open-source project out there seem to be able to muddle along without face-to-face communication.
Besides projects are supposed to be a team effort and as a member of the team you should care what other people are doing and what issues they may be running into.
That's your job as project lead.
... and no need to put added pressure on any dev by suddenly making daily inquiries about their progress.
Then you explain to them why you are making such inquiries and, if they'd like them to stop, what they should do about it.
Open source projects are a different beast that don't operate under the same constraints that a commercial project does. You lose some efficiencies in terms of communication but for projects like the Linux kernel or Apache you have potentially an unlimited pool of developers and much more flexibility as to what gets delivered when. It should also be pointed out that for every open source success story like Apache or Linux there's lots of stuff that dies on the vine or never gets off the ground.
Look, it's clear that you're not happy with an Agile approach and some people just don't work well in that environment. It seems to me though that people who only give a crap about their part of the project and resist any face to face communication in favor of email are limited in the sorts of projects they can work on successfully.