My guess is that the plants will eventually begin to show phosphorus (P) deficiency symptoms.So I went to my media shelf and picked up my jar of phosban and measured out the amount needed for a 30c. Within 3 days all the hair algae in the plants where gone. An now on my second month of running all algae are gone even in the glassware in the tank.
In the case of Fe it is highly immobile in the plant, so even when iron ions (Fe++(+)) become available it takes some time before the plant can produce new non-iron deficient leaves.After 7-10 days between water changes my glass was spotlessly clean and never had to even wipe it off. After dosing some additional Iron (only about 2ml/day) my glass became green after 4 days. After 7 days I had to scrape it off as it looked disgusting. Now stopped dosing it again and my glass is clean again.