WD wrote:

My anubias, swords, and Java fern have been growing wonderfully for a
couple months now. I have been using Flourish and Trace, more or less to
package directions. Lately, my anubias has been turning a reddish-yellow. Is
iron deficiency likely? None of the local LFS have iron test kits, in fact
most of them have no idea what I'm talking about. Mail order only option.

75gallon
moderately planted, heavy bio-load, gravel sub, wet/dry sump overflow.
3x40 day-max 1x40 something else, yellowish light. Forgotg
amo:0
nitrite:0
nitrate:10ppm
Ph:7.0
tmp:78f

Flourish provides what we call "trace elements" on this list, except it contains
no iron. Flourish Trace provides just a few things that are used up, and it is
probably not helping you.

If using the Flourish family, you will probably need to dose Potassium, from
Flourish Potassium or dry K2SO4. If your water is low on iron, you will need to
dose Flourish Iron.

Another alternative is to switch to PMDD, which uses inexpensive dry fertilizers
and chemicals, and which includes Iron, Potassium and optionally Nitrate.

Start reading he

http://www.thekrib.com/Plants/Fertilizer/