I apologize, but I don't know what meds your Lucky is taking. Perhaps Phenobarbital or valium? If so, you will want to work out a tapering dose with your vet rather than go cold turkey. The cold turkey approach can sometimes trigger seizures.
Also, while you may well find that Lucky's seizures were indeed related to diet and medication reaction, there is the possibility that now that Lucky's brain has essentially "learned" how to have a seizure, it may continue to do so even in the absence of Flagyll and other original triggers. I don't mean that to be a discouraging comment at all, just a mention so that if it happens you will not be shocked or unduly frightened. With some dogs, an exposure to something that triggers seizures seems to lastingly lower the brain's seizure threshold, making the dog more vulnerable to seizures than he/she before the exposure to the original trigger.
Best wishes to you and Lucky in trying to get off the anti-epileptic medications. Keep us posted, will you?
--Lucy