What are the stains from? If it is just a light rust circle from the bottom of a can, you may be able to just take a brush and water and scrub it off.

Rust remover! Barkeepers Friend will work.
Make a paste and put it on, let it sit and hose off.....repeat if necessary.
Linda C

Try the Bartender's Friend first, but if that doesn't work here is a more dangerous solution. While wearing rubber gloves and eye protection, pour a small amount of 'The Works' toilet bowl cleaner - which is actually hydrochloric acid (Mercuric Acid) - on the stain and it will disappear immediately. Be VERY careful with this and make sure that it doesn't get on anything else but the stone. Rinse very well - better to CAREFULLY pour water on the acid to delute it than to use a hose that can splatter.

Note: 'The Works' has different product lines for cleaning tub & tile, for example. What I'm talking about here is the 'for toilet bowl only' product.

Hydrochloric acid is also called muriatic acid.
I wouldn't be using it on my bluestone patio. Sure it will remove the rust stains, but depending on what kind of blue stone you have it may etch the stone.
If you have any stone left over, try it there first.
Linda C

I've used lemon juice and salt and sit in sun (or not) on clothing to remove rust stains. (old dryer, damp clothes in dryer overnight left rust stains because drum was bad, got new dryer) It took a few treatments but mostly worked.

Thanks everyone! Very helpful. The rust is from a metal pan which was placed under heavy planters