Browns stains on washing?

We have been getting brown stains on washing for years now. These stains were mainly on cotton type clothes, T shirts etc.On our original washing machine we had it repaired a number of times, new drum, new bushes but the stains always came back. We have bought a new washing machine and the same thing is happening again.
We had have a water softner and do not know whether this may have something to do with it. We also thought that it may be a combination of deodorant on clothes, but are not sure now.
Can any body help. We use powder and also liquid for washing the clothes.