I am looking to help out my semi- planted 30 gallon aquarium. I do not have a CO2 system or use any additives at this point. I was told Leaf Zone would be good for the plants, however; someone also recommend Seachem flourish or flourish excel. Any suggestions?
Excel is not a fertilizer, it's a carbon substitute that is supposed to replace CO2 but doesn't. I believe it may help a tiny bit, and it is also great at killing algae (it's only ingredient is a biocide called glutaraldehyde)
To answer your question, I would say leaf zone.
It has only iron and pottassium yes but from what I've been able to research those are the two most important nutrients for green leaves and plant growth.
I'm NOT saying other nutrients aren't needed but there's a reason the majority of fertilizers have iron and potassium even if it doesn't have the other ones.
Do you know your nitrate and phosphorous levels? If the tank is lightly stocked with fish and with plenty of plants their levels might be low enough to use an all-in-one (macro + micro nutrient) fertiliser at low light dose rates.