looks like a sulfer deficiency. iron deficiency is also possible, but trace element issues are rare in soil and more often related to ph or nute lockout.
if you've bombed it with calcium, that can lock out Fe. Too high phosphorous can also do it.
the way it is progressing, it looks like you need a bit more S, though. yellowing top-down and from petiole out on leaf. it's a fairly unique progression.