Three of the  following four letter-clusters are a like in a certain way and one is different.  Pick the odd one out.

FHG WZY LON ADC

FHG

FHG = F → (+2) → H → (-1) → G (THIS IS ODD) WZY = W → (+3) → Z → (-1) → Y LON = L → (+3) → O → (-1) → N ADC = A → (+3) → H → (-1) → C