Nitrogen Toxicity First weeks of Flowering - What should I do?

Oh, I just harvested MY Tangerine Dream! You'll love it! But to your issue, if you are certain you've got nitrogen toxicity, then you really should flush to get rid of all the nutes that have built up. I assume you know what a flush is but in case you don't, you'll need to water with 3x the size of the pot - so a 3 gallon pot would take 9 gallons of PH'd water through it to flush it out. I'm NOT convinced you have what you think you have... Your lights are FAR FAR FAR too close to your plant and I think this is heat/light stress... you're rather burning the upper leaves off! The other problem might be that you're under/over watering. If these were my plants, here's what I would do: I would raise the lights to be 24"-30" from the plant first! They're pretty short and this will encourage them to stretch which you're going to want the further into flower you get so that air flow isn't restricted. I would check the PH of my runoff (needs to be between 6.0 and 6.5) and if it's out of range, I would flush and go gently (1/2 strength) with the nutes when you add them again (then go ahead with normal feeding the next time). Tangerine Dream starts really wanting a lot of water when they get to flowering stage so don't be shy (but don't keep it water logged, either)... make sure the pot is nice and light when you want to water/feed (check it daily!) and then make sure you're getting about 20% runoff checking the PH of that runoff for at least the next couple of waterings/feeding. I think this will solve all your problems even if the issue is nitrogen toxicity... Good luck, enjoy the grow! My two plants brought in almost 10oz dry!

Get an EC pen to confirm the concentration of the feed solution you are providing them. Autos feed less heavy vs their photoperiod counterparts. https://www.autoflower.net/forums/threads/med-man-method-feeding-chart-ppm-ec.47856/ Good Luck!

Yo veo bastante bien a tus plantas, están hermosas! Lo que yo haría seria subir un poco el pH y no colocar nitrógeno por un par de riegos hasta que se recupere, lo bueno de todo es que te diste cuenta a tiempo. Buenos humos 👌