Bass, buy a box or bottle of Iron sulphate or iron chelate. Apply 3 times a year. This is not to be used in substitute for fertilizer. After the problem is resolved, apply again as a preventative.
I've never tried liquid Ironite, but it may work as good as the powder. Your problem is an easy one, Bass.

Leaves can pale for many reasons like insects, or other mineral definciencies. But since the veins are deep green it's probably an iron problem.Try the iron and see what happens..Toni

You can also try some Miracle-Grow Acid type fertilizer ( formerly Miracid). May transiently help with pH issues that could interfere with uptake (as well as provide a little iron--won't hurt :). Tap water is often slightly basic so that it doesn't precipitate out goodies from the pipes for us to ingest. Yummy.

I have difficulty understanding what Tapla is saying.
Anybody wants to interpret what he is saying?

I think hes basically saying that the iron and manganese have become "locked" in the soil. Even though they are present they are not available for the plants use. This would happen if the soil was too alkaline or too acid.
Andi

Heres a good link that explains it better

Here is a link that might be useful: Soil pH

I have tried chelated Iron on leaves onces... It causes a dark stain on the leaves.
I applied aluminium solphate, (it looks almost like salt), directly to container soil.
Tapla, I diffinitly use well drained soil on all my containerized trees. Bonsai, Citrus, Figs. I try to avoid peat moss it's too wet, even though it is helpful with lowering ph in citrus and azaleas.

Bass

Thanks Andi.
That helps a lot.

Bass, I reccommend using Iron dirctly in soil, not on leaves..I've never tried a foliar iron spray, but thanks for the warning..