My guess would be that the medicine has degraded past peak maturation. Which makes sense considering you grew what's supposed to be 100% indica (we all know indica's ripen quicker), and flowered it for 2-3 more weeks than the "recommended flowering time". Perhaps the peak THC content was reached at week 8 (roughly), given another 1-2 weeks of high energy light probably degraded the medicine from mostly THC to mostly CBN which is a much more mild psychoactive medicinal analogue. I suppose this would be the risk with such a high percentage of indica in its genes.
Since we would need a GC-MS or H-NMR reading to see what compound dominates the mixture, and see what it REALLY looks like, my opinion is that the color of the trichomes are not fully indicative of the peak psychoactive state of the mixture of compounds that resides within the trichome itself. You would need much more analytical means to be sure, so I suppose that's sort of the gamble with growing a nearly pure indica, and basing the analysis off of basically a color test. Had you sampled the crop around week ~8?
Anyway just my two cents, hope no one is offended by my words