I think that some cryptocorynes can be a bit sensitive to environmental change (being moved, temperature changes etc.). I recently half-emptied one of my tanks so that I could replant my Lilaeopsis, so the heater was turned off over night as it was late in the evening when I did it and I didn't want to wake everyone in the house up by refilling the tank. Now that my tank is full again and at 26C, the Cryptocoryne wendtii 'Mi Oya' seems to be dying back a little. I'm getting a couple of leaves that are 'melting' away from the tips, which is really annoying. I think it's pretty normal though for crypts to be sensitive to such things.
I can't really comment on what to do about it though... I just added a root tab and am giving it TLC to see if it perks up again once it's re-settled itself.