Okay, I test them insidthe instrument, I'm filing the end to sharpen them. I've managed to tune almost all the others just fine so there's no problem with the reedplan, and the reeds fit fine in the slots. The tongues are set right and are clean, the valves are new and in the right position. They are on the chambered side of the pan so it has nothing to do with valve pins. I've managed to tune the other reeds, and have been trying with these for a while but they still do the same thing so I thought it would be best to ask before I wear them away too much since, as you can see with the d#/eb thing, I am pretty good at missing glaringly obvious things. The action board is all fine too, and the adjacent notes in the same chamber are both fine.
I also can't see any cracks or damage to the tongue, and they have not been filed a lot, so I'm pretty sure it's not fatigue/damage causing it. (Reeds are steel, by the way.)