I would check all of the connections and cables first. It sounds like you may be splitting the signal too many times. Have you tried using each television by itself? You should terminate the other lines when/if you do.
Im not confidant that the amp is causing your problems. Unless you have internet or phone, then your upstream might be out of wack, but i would take a guess and say its a signal issue, you do have an amp in the first place after all, the 'correct' way to fix the problem is to have your house rewired with RG6