That makes sense, so some type of roundworm, there are quite a few species of roundworm. Does knowing the species of roundworm help, my personal opinion is no.
So does the bombing routine (essential oils) working? My suspicion is that what you doing would cover a wide spectrum of possibilities. You could look at abendazole as a possibility.
You could try adding goldenseal leaf (not root) which has compounds that stop resistance, regular hemp oil (not marijuana oil) has cannabinoids that stop resistance as well.