Odds are, it's something

Odds are, it's something internal to your application. GPUImage is an ARC-enabled framework, so it always uses ARC for its own compilation. The only thing you've changed by moving your application to ARC is your application itself.

I'd look for retain cycles, which can be very subtle to track down. The heap shot functionality in the Allocations instrument is what I rely on to see where I'm accumulating memory due to cycles like this. Take heap shots before and after every repeat action that could cause memory buildup.

Sunset Lake Software - Comments for "Converting to ARC"

Odds are, it's something