how do you remove / limit the damage of mildew?

[EverythingsPink]

Its on the inside of our tent. Lots of little black spots but don't want it to get worse. Have already washed it in the washing machine (with powder at 30deg) and no difference.

Tried putting some diluted Milton on it, and still no difference.

Any suggestions please?

I don't think there's much you can do except make sure it is bone dry when you put it away and store it in a very dry place. If you put bleach etc on it will weaken the fabric.