wall tiles in shower

[greengrass]

I can't understand the black mould appearing on the trim and tiles at edge of the shower tray & wall tiles. It's a bugger to keep up with.
What's best method of cleaning. I used a supposedly mould free silione to fit the trim but when removed to re-bed all silcone underneath was black. So much for mould free!.

Also the best attachement for either Dremel or a battery drill for removing grout which is turning yellowish. Can't use had cutters have some degree of arthritis in hand and would exacerbate the pain Many thanks