Cat food rebellion

I recently bought a new bag of Purina dry cat food - seafood flavor (which I bought the exact same of last month) and not 1 of my 3 cats is happy to eat it. For over 4 days now my cats have point blank refused to eat the pellets. Please explain.... same flavor..same brand..a month apart... doesn't make any sense. My cats only eat dry food and normal are not fussy.