Originally Posted by Boredomb
Well if it is excess Iron then it must be coming from my soil substrate but heres the deal. I have not and I am ashamed to say but I haven't actually dosed any fertilizer for about 3 weeks now. There are some root tablets there by the Sword. I know there is at least 1 if not 2 near by the sword. This is why I just assumed it was a deficiency not an excess hmmmm .... Maybe to many tablets near by but those are from Flourish so they shouldn't be unbalanced or have more iron then the rest of the nutrients. I also don't dose just iron or haven't added anything like clay for Iron. So not sure there.
My GH is 10 the best I can remember. Also didn't mention the liquid fertilizer is Flourish Comprehensive.
Diagnosing nutrient issues is not easy, as many different deficiencies can have much the same appearance. Deficiencies and excesses can also be caused by some other nutrient being in excess or deficient. Brown blotches can be caused by an accumulation of iron when calcium is deficient, but also it may indicate iron deficiency, and I believe potassium deficiency. Knowing which this may be can sometimes require experimenting unless a deficiency of one of these is a known certainty. In my case when my swords all developed these brown blotches it turned out to be calcium deficiency allowing iron to accumulate.
In your case I would doubt this as the GH is 10 which is fine for calcium and likely magnesium. Potassium may be deficient however, as this would result from the lack of liquid fertilizers which you've mentioned. Plants can only take up potassium as an ion directly from the water, not the substrate. Potassium in the substrate is thought to possibly increase the availability of ammonium to plant roots.
If this is something that was not occurring previously, I would simply get back to dosing Flourish Comp once or twice a week and after a couple weeks observe the plants' reaction. This deficiency is usually on old leaves (outer leaves) first, so if newer leaves (those within the crown) do not show this, problem solved. The existing blotchy leaves will not change, and it is up to you to leave them or cut them off. Some nutrients within the leaves are mobile, meaning the plant can transfer them from old leaves to new growth. If the stem at the crown is brown, the leaf is basically dead and with no connecting veins this can't occur so removal of the leaf is best. But if the stem is still white then the plant is able to move nutrients up and down.
It only takes a couple weeks in my experience for issues to become evidence due to nutrient changes, so there you are.