Cats feeding why are my cats so fussy,its driving me mad?

i have two cats ,i regulary change there food as they just look at the food and look at me as though to say ,hey whats this,i aint having none of that,im in uk so they eat dried food go cat, eukanuba ,other makes of dried food with carrotts and all.they eat whiskas tins whiskas pouches,kitekat felix tins and pouches they do about two or three days,and then turn there nose up at them...whats going on is it just my cats ....is there anything else i can try,anybody else got feeding problems with there cats ..any ideas cheers anybody xxx emma x