Mould/Black marks in washing in Bosch WFF2001

Sorry if this is a noob-type question

We have a Bosch WFF2001 – about 8 years old.

Has been working fine for a number of years, however over the last 6-ish months have been noticing black marks on some of the washing.

We typically use non-bio liquid detergent + fabric conditioner (If the clothes are not going to be tumble-dried).

The soap drawer does get cleaned out occasionally, and we do have some black mildew-type marks on the door rubber.

I’ve read through some of the FAQs on this site, and have tried the following;

Wiped around the door seal & the soap drawer with a bleach solution, and then done a maintenance wash (using ariel powder in the drawer).

This has removed SOME of the mould, and around the door seal it is a LOT cleaner.

However there still seems to be some residual mould coming from somewhere – in the last wash there was quite a few bits of mould left on the washing.

What I want to know is :

1. have we caused terminal damage to our washer (we live in a hard-water area) because the mould we seem to have must be “living” in an inaccessable part of the machine. – or is it a “simple” case of just replacing the door seal.

2. The last load of washing was a very expensive set of sheets which now seem to have “speckles” of mould all over them – the mould just seems to be sitting on top because it will come off if scratched with a nail.
– is it ok to tumble-dry these sheets (They went through the wash twice), or will this “fix” the mould to the sheets ?

Ta.