Studies have shown that there are little to no differences between a flushed plant vs not, in dry matter or cannabinoid. So if we aren't flushing the plant, we are flushing our wallet instead. Which leads me to my second point, P and K aren't really needed, even in flowering, and they will either leach in a pond or accumulate in the plant
Most people won't taste it, even an unflushed plant. But i do taste the coco when i vape buds grown in it - that AVB after taste. And i do find that a well flushed plant is much less harsh on my throat and lungs - i smoke a lot. Some people can even blindly recognize where a small wine is grown
In your situation, i don't think that you will see many yellowing leaves even with a 2 week flush, leaves are clawing and that nitrogen in excess will never be metabolized. Defoliation may help but also will reduce the overall metabolism, and they would need it to recover. But it's still better than nothing imho
So in short flushing and a proper nutrition can give you a much better smoke and will save you substantial money