I checked out Spring and Synchronic, because I'm a big fan of the Endless and Resolution. I think the latter films are the better movies from Writer/Director Justin Benson. But the former are both pretty cool in their own right.
Spring's the weakest of the bunch IMO. It's about a grieving dude who's aimless and gets into some trouble. So he runs to Italy, where he meets and starts dating a local woman. But she's got way more going on than he realizes. This is a romance with a horror backdrop. The plot feels a bit wonky at times, but it has some cool ideas.
Synchronic is the least horror of the four movies. Two paramedics keep coming across a new synthetic drug at these unexplainable deaths. Meanwhile, one of the paramedics finds out he's sick and the other's daughter goes missing with signs that she may have taken that sketchy synthetic drug.
Synchronic is a pretty cool concept, with Anthony Mackie doing a good job as the lead. There's a bit of mystery early and then a pretty cool discovery process that follows. The only reason I prefer Resolution and Endless is that they're straight horror movies. But Justin Benson did a great job again. I know he's had a hand in some Marvel tv episodes, but I hope he blesses us with another horror.