Iron Out, or something similar

Looking for Iron (or Rust Out), liquid or powder. Found on AMZN but I'm guess with all the hard water here, I can find it a lot cheaper locally.

If you are trying to remove rust stains oxalic acid may be what you want. Among its uses are cleanser and wood bleach. Oxalic acid is the ingredient that makes Barkeepers Friend or Zud better than Comet. Oxalic acid is what gives rhubarb its distinctive flavor. You may be able to find it at a pharmacy or a hardware store.

Actually looking for it to bring some white t-shirts back to life.  Used bleach on them but due to hard water, they went pinkish.  Research said to whiten them in hard water, use something like this.  

Anyone have any alternatives, or what I should look for on the laundry aisle?

You might want to pick up some 20 Mule Team Borax available at SuperLake.
Because the water is so hard here, I started using it about five years ago. Every load of laundry gets detergent, oxyclean and borax. I leave the lid up so the load can go through the first cycle and then stops. When it stops, I shut it off and let is soak for a few hours. Then I turn the knob back to the beginning of the cycle and start over.
My clothes kept getting cleaner over a couple of weeks when I first started doing this. Now they're just always clean and fresh smelling.
It is my preferred method of doing laundry but I don't think you can do the "pause to soak" with a front loader.
And both borax and oxyclean are septic tank friendly.

But will Borax and/or Oxyclean take the pink out of the (formerly) white t-shirts?? That's my main concern now. I did a whole load of them!

The Iron Out claims it will.

I have no idea. The Iron Out is available at Amazon Mexico. But don't use bleach since it rots the fabric.
https://www.amazon.com.mx/Iron-Out-IO30N-28-Oz/dp/B00TUWIRH2/ref=sr_1_1?crid=TVIDUOZTHP6V&keywords=iron+out&qid=1649342584&sprefix=Iron+out%2Caps%2C97&sr=8-1