Nute burn or something else?

That (58f)is way too cold. And purpleing due to cold is not what you are thinking it will be, especially with the flowers still growing. Temperature swings like that will lead to excessive stretching and very, very low bud density (comparatively).
Definitely insulate the window. And do your best to bring up and stabilize the temperature and humidity. These things are important for success.

SpawnOfShulgin said:

FFOF with blue planet nutes fed according to label but used 50% less micro in the last feeding to reduce Nitrogen because I figured FFOF has enough N for the rest of flower.

Thanks in advance.

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Plants look really good , the tips look alittle burned but buds look fat and foliage looks green as well , if it were me I’d check ph , and light distance , a lot of times when your tips are burned your lights are too close and or too hot , maybe tais them or turn the intensity down.