Hey there, gotta disagree with folks here, that's potassium deficiency as you can see from the colorful way the plant is wilting. That's because in flower you need more K, the biggest flower needs the most K, that one is fat but cant get enough K that's why it's cannabalising the leaf. You're really doing perfect so far in the grow so i dont really know how you want to "fix" this which is all just due to the plant going into overdrive . I wouldnt touch it unless it got worse, does that make sense? Hope this helps ! 🚀