A flush should be fine - they dont look quite ready yet though.

the rust spots on the edges are fine - the leaves normally start to deteriate near the end of flowering. - how many weeks have they been in flower now?

Do you have a 300x zoom lens at all? By looking at the trichome heads you can see weather they are clear/cloudy/amber. The best time to harvest is when the majority are clear with around 30% amber.

Also feed the plant nothing but water for the final 2 weeks of its life + nothing in the final 7 days - flush then cut + hang to dry!

P.S. That is guna be a nice smoke! - lots of resin on them buds!