significant lag on perfectly quantized MIDI Q-Sampler drums during playback

I loaded some one-shot drum sounds into the Q sampler and created a beat but there is a significant lag on the drums during playback, even after completely snapping the notes to the grid; there's no latency in the monitoring, the drums are just lagging when they shouldn't be. There is no space before the drum sounds in the sampler itself. I have the whole kit in a summing stack with UA compressors running on individual drums. I have an EQ on the summing stack and on individual drums. I am running the kit parallel into the Abbey Chambers plugin for a slight room sound. Is this a problem with processing speed or something? how can I fix this?