Lets clear up a few points here. First.
Flourish Excell is bio-available carbon and nothing More. no iron no anything else.
Flourish Iron is iron
Flourish is a trace element mix which has some iron but typically not enough unless you have decent amounts of iron in your tap water.
Plants need three macro nutrients.
Nitrogen
Pottasium
Phosphate
Flourish makes all of these in ready to use products.
Pottassium defeciency will cause holes in the leaves, especially in Annubias, These holes will eventually turen yellow around the edges, but pottassium doesn't show up as yellow leaves.
Nitrogen defeciency will cause a lack of color, usually in older leaves.
Iron Defeciency will look similar to Nitrogen defeciency most of the time, But causes new leaves to grow in yellow.
Nitrate test kits are available and everyone should really own one in all honesty whether you have plants or not.
The three macro nutrients will often come in via fish food (Converted to fish waste) and possibly tap water so in a low tech low light slow Growth tank most folks don't have to dose. In higher light tanks dosing is usually required.
In addition to The Three macros, plants need a good trace mix (To priovide micro elements) a carbon source and light.
It really sounds like the issue is iron. try increasing your trace dosing a bit, and supplementing with iron as well. I'll hazard a guess that things will perk up.
Dave
