How to remove rust stains on vinyl siding

[How to remove rust stains on vinyl siding]

I tried the safe restore because I had it on hand for window restoration. It removed the extreme rust very, very quickly. Then I rinsed it with ammonia water. One cup per gallon. Turned out perfectly regarding the rust stains. Now here was my problem. Strait 6% bleach did not remove the Alabama red mud stains, nor did butyl based, nor Sodium Hydroxide cleaners nor anything else I had available. But the acid in safe restore made the white vinyl look like new. What would be my best option for washing an entire building following a high PH wash. (I also added my signature to this posting hope it shows)

[How to remove rust stains on vinyl siding]

What is the best/safest way to remove rust stains on white vinyl siding. I have an apartment complex that is stained under all of the through the wall heating/AC units.

There are about 250 units. I believe it is rust from draining condensate.