How do I stop my Hygena dishwasher depositing white powder all over dishes?

My Hygena dishwasher (model APL812411)is around 5 yrs old and has been very reliable until
recently. It has started to deposit, white powder, presumably limescale,
all over the clean dishes. It is really difficult to get off and is not
just a little bit, it leaves a completed film over everything. It is also
depositing it on the runners of the racks and they are then difficult to
slide open. I tried dishwasher cleaner and lime-scale remover, and even
tried cleaning the element but nothing has worked. Has anyone any ideas
please? Has something broken do you think?