It could be both manganese and iron deficiency. An acid soil is not a guarantee for a correct absorption of micro elements. There are other factors, like oxygen in the soil or a dry or excessively wet soil. I have a Buddha's Hand on macrophylla rootstock in a pot, with acid soil (PH 5, 5), fertilized with osmocote for citrus and shows similar deficiencies. I have corrected it with a foliar fertilizer. You will see fast and excellent results, believe me.
In any case, in the long-term you must fertilize the soil with a good fertilizer.
Dyna gro Foliage Pro is a frequently recommended fertilizer here.
I have not tried it, there is not that brand in my country.

This post was edited by axier on Sat, Sep 13, 14 at 5:31

Thanks Axier,

So, as a foliar spray, does it need to be a specific fertiliser, or will a general purpose do ..... the point being that it is foliar, rather than root drenching?

Dyna gro Foliage Pro is valid for both soil and foliar.
If you use other fertiliser, it is preferable that it is recommended for foliar application and with micro elements., and with a N-P-K ratio in the proportion of 3-1-2 to 5-2-3.
In any case, I have more experience with other fruit trees than with citrus.
Wait for opinion of citrus experts. Although I suppose it will not differ much from what I have told you.

This post was edited by axier on Sat, Sep 13, 14 at 9:59