Spotting 8 dp iui

I am 8 dp <a href="https://glowing.com/glow-fertility-program">iui</a> but brown discharge from 6 dp <a href="https://glowing.com/glow-fertility-program">iui</a>. What may be the reason. Will implantation bleeding last this much days. Usually i spot 2 or three days before period. But this is too early.