Try zooming in on phone camera -- If you can see the stalks and head, you can tell color (google 'trichome' for a reference of what i speak of)
this is 40-some days? so, you have 3 weeks left or so. It can make it, i bet. so, don't worry too much if you cant fix it perfectly. They will start to yellow and detoriorate naturally toward end, too, but that's looking like nute burn more than anything else to me.