Iron removal filter in Kumbakonam, Tamil Nadu : Usage issues & doubts

I live in a village near Kumbakonam, Tamil Nadu in an apartment complex. Our Ground water has iron (3.1 mg/litre). We have fitted an Iron Removal Filter about a month back. After 2 days of installing the Iron Removal Filter, I took filtered water sample and got it tested. The result shows that our water still has 1.2 mg/litre iron. Also there is 25 Turbidity.

I also did a simple test at home like I took filtered water in a bucket and after 6 hours I saw that the colour of the water changed to mild yellowish and it smelled. We do backwash and rinse on a daily basis. During Backwashing I see the colour of the backwashed water is dark brown indicating that the filter does its work.

I took the report to the filter manufacturer and he insists that his filter does the job neatly in other installations.
Yesterday (after about 20 days of installing and testing), I took a bucketful of water and after 6 hours saw no no colour change and no odour. But I am yet to test the water in a laboratory for proper chemical analysis.

My question:
Assuming the test result may show no iron in our filter water, Is there any stabilizing time for the media in filter to come to 100% efficiency.
Will it start work perfectly after some time only.
Were we too hurried when we tested water after only 2 days of installation?

Any help will be appreciated.

R Balaji