What size tank? Parameters? How long ago did you move them?
Unless you've seen the tetras harassing the cories, I would guess they are timid because of the new environment. Although serpaes are notorious fin-nippers, I've never really seen them go after bottom-feeders.
Is it a 20 long or high? I'de add 3-4 more Serpae and 3-4 more Corys. They will then most likely keep to themselves and harass each other instead of other tank mates. I have a 55 with 5 Serpae a Pearl gouramI 12 Vonrio tetras some guppies some Corys and a couple other various inhabitants and my Serps have never gone after anyone except their own. Not damaging just what appears "pecking order fun" and i've had them over 2 years. But at the same time my tank is heavily planted so there are blind spots and plenty of cover. Couple pics of my 55 and my Vonrio school