"Dahlia's second potion increased the duration that I was invisible to the Infected, but it drastically slowed my sense of time. Still, it seems like the effets are becoming less of a hinderance. Perhaps the next one will be free of side effects."
All you need to complete this side quest is find a bomber and wait for it to kill itself, so you can search it. The Stuffed Turtle quarantine challenge is the best place to acquire one, since a bomber always spawns, and even after it explodes, virals will not spawn due to the sound, though virals will crawl out under the boarded doorway so be wary.
Then go back to Dahlia and collect potion and blueprint.
