Yellow mottling on Passiflora

Hi there! I've got a Passiflora 'Coral Seas' and have noticed that some of the older leaves are mottling (bloches) yellow in between the veins. I'm thinking this is either a nitrogen deficiency or micronutrient deficiency. I was going to treat it as such, but thought I'd drop a note in here and see if anyone has experience with this problem in Passiflora.

Thanks for your help!
Mitch