When you get a chance, you may want to go find an old CD/DVD and observe the red light as it's reflected off the recording side of the disc. The disc will act as a simple prism and break the light up into discreet color bands.
Look closely and make certain your LEDs are not also emitting small slivers of blue and/or green light. Too faint to see with the naked eye, but enough to sometimes cause slight fogging in your print highlights. It's not unusual for red LEDs to do this, regardless of what the specs say.
My 635nm red LEDs showed both blue and green spikes. If yours do as well you may need to add a single layer of Rubylith as a filter. This will fix the problem. Also make sure you perform a pre-fogged safelight test with whatever paper you are using.