Is this a pH problem or a magnesium one?

Hi, I was wondering if anyone could help. My plants are looking ok, but some of the lower leaves are wrinkled and the new growth coming thru is a little on the yellow side... This is not continuing down thru the rest of the plant yet... But I don't know...
I am using Canna Flores A & B with Cannaboost with the occasional few mls of Cannazym... I usually don't have a problem but this time...

umm well what's your ph? It can obviously be both ph and mag probs. yellowing is usually a nitrogen def, but if you are having multiple issues and are feeding regularly, ph is where I would start.