Hi all,
The recipe in Johny70's post would work, as it supplies all the macro and micro nutrients needed for plant growth, if you just want to treat the symptoms you've got of green veins and yellow leaves "
interveinal chlorosis" is either magnesium (Mg) or iron (Fe) deficiency.
You can treat the magnesium with "Epsom salts" (magnesium sulphate) and the iron with iron chelate (FeEDTA), the cheapest form of iron chelates will probably be as "Sequestrene" or similar for watering on Azaleas, Gardenias, citrus etc. You can't used an iron compound (like iron sulphate), as iron compounds are mainly insoluble, and the Fe2+ ions will form iron phosphates etc. and precipitate out, it has to be "chelated".
You can buy aquarium ones, but they will be very expensive compared to buying the compounds themselves.
Iron deficiency <
http://www.uky.edu/Ag/kpn/kpn_09/Images/032409 Hartman Rhodo Fe deficiency (Kaiser) H17-73.jpg>
Magnesium
<
http://www.agnet.org/images/library/bc53002f4.jpg>
The other problem is that Anubias are very slow growing, so if it is iron deficiency only the new leaves will be dark green, and won't effect the leaves it's already got. However if it's magnesium you should see an instant effect, as magnesium is mobile in the plant and will move to the deficient leaves.
I'd try Epsom salts for starters, you want about 20ppm (mg/l) magnesium, if that doesn't show any effect try the iron chelate, for iron you need a very small amount only 1 or 2 ppm. PM me with what it says on the containers you bought and I'll do the calculation for you if your not sure how to do it.
cheers Darrel