Aahhh, one of my favourite strains! I would be concerned that is is the beginning of mould/fungi, and would be keeping moisture in the grow area to a minimum, and possibly checking your flower for any mould/fungus growing within the flowers, and if found, removing the affected parts immediately, before it spreads and you could potentially lose even more. Knowing how solid and dense Amnesia Haze is, this would be my first concern. Seeing as this part is closest to the light where it is the warmest, would suggest to me it is also the most humid spot too, leading to possible mould/fungus issues. Your plant looks to me as being ready to harvest, so it may be wise to do that sooner rather than later, especially if you do diagnose the problem as mould/fungus. Better to get what you can while it is still relatively healthy, than wait too long and letting any problems potentially spread throughout everything. I have never had any problems with growing this strain outdoors, even in temperatures as high as 45+ Celsius, so I doubt it is heat stress, unless there is no or very little air movement. Hope this helps.... Organoman.
PS - see my diary "How Sweet it is" for some outdoor Amnesia Haze pictures.