I’ve already made a flush finishing at 500 ppm, do i have to make another flush before harvesting? On my schedule harvest is this sunday!

Around 100PPM left is general guidance. The key is that the leaves have faded - like yours have. I wouldn't bother to flush again if I were you. Your plants look great!

From what I’m gathering, you want 100ppm or below for proper Non chlorophyll taste of the buds. then again this is is my first grow and this answer is from research only. might wanna wait for someone else with proper years of knowledge.