With high GH, iron from DTPA would be available for longer than Iron from EDTA found/used in many trace mixes.
I have 12 dgh ,and found that adding a bit of Iron from DTPA ( www.Greenleaf
aquariums) in addition to the iron EDTA in CSM+B helped the ludwigia repens ,and ehinodorus red flame appear more red.
I kept trying to boost Iron by increasing the CSM+B, but a plant guru told me that this could lead to toxicities possibly ,and that the iron in CSM+B (EDTA) does not hang around long in hard water. Heard anywhere from 2 to 4 day's.
As I only dose fertz once a week(low tech),I think I was limiting iron availalble and was suggested to source some iron from DTPA which is more suited for harder water.
After trying the DTPA the red hues to a few plant's seemed to improve and stay more red throughout the week (To my eye's anyway).
Course if one is dosing daily or every other day ,it might not make much of a difference ,but with once weekly fertilizing, I felt it could not hurt to try Fe from DTPA.
I still add CSM+B once a week day after macro's but I also add a bit of DTPA and will stick with it after noting improvement.
I have had anubia/crypt's just melt away after H202 bath for too long or too concentrated.
Now I just toss plant's with algae on leaves into tank holding long finned albino baby bristlenose and cherry shrimp,and they clean the leaves within a day or two.