Ask Mr. Smarty Plants

You are correct, cement leaching is way out of our field of expertise. The flowers you are referring to are not even natives of North America, and/or are so extensively hybridized that we would not be able to identify their ancestry. And you should remember that when you ask questions in a nursery, especially one not completely plant-related such as this one, that is not in their range of expertise, either.

We're going to offer you some alternative solutions, and perhaps you can work out what your problem is. Are they in sun or shade? We believe both the plants you are referring to are sun plants. Do they have heavy mulching over their roots, or rhizomes? Iris, in particular, can rot if their rhizomes are heavily covered-they need some air. 

Since you say some of the same plants a few feet away are doing fine, we would suggest you simply move the plants you are concerned with. That will give you time to try to solve the problem without sacrificing plants you wish to save. If they suffer from transplant shock, this is not going to help them, but likely won't kill them. Just trim off any foliage that is looking bad and replant in a more suitable place.

Now, to find out what the problem is with the wall. You need to know what is going on with the soil; perhaps in the process of building the wall, some toxic material got into the soil that is now making itself felt. You can get materials and instructions for getting a soil test by contacting the Colorado State University Extension Office, El Paso County. Dig down in there, see if you can find rubble or powdery material that looks like it doesn't belong.

And, finally, we Googled on "concrete leaching into soil" and got a number of references. One that we followed up briefly said concrete always leaches some lime. If this is the case, you can try neutralizing it with something that is naturally acidic, such as pine bark mulch or compost. We would suggest you continue to pursue that line of inquiry, starting with the concrete, and  follow up leads on the Internet.