Is it salt ?

I have a similar problem with our dishwasher, it had been working fine for 5 years and then suddenly started leaving salt residue on everything (though it was only obvious on some items).

I think what has happened is the water softener in our dishwasher has failed in some way. I solved the problem by stopping filling the salt dispenser. It look a dozen washes for all the salt in the salt dispenser to go, but after that the residue went away.

It seems to wash about as well as it ever did.

Our water isn't that hard and the 4-in-1 tablets have salt in them anyway, so I guess we have been pointlessly filling our salt dispenser with salt for 5 years !