Two questions

I have two plants that looked hungry (leaves are light on top, dark on bottom) no other symptoms. I carefully raised their ppm's twice and light leaves started purpling. indicative of lock out. There are some leaves (very little) with brown tips that look like overfeeding. I checked runoff and the ppm was the same that i'd watered in, no excess salts. ph was 6.8 instead of 6.5 so i adjusted it. Sounds like overfeeding but it can't be. I have the same strains in the veg room at the same ppm's. I've had problems getting these two plants to take more food, unless i've missread them and underfeeding looks similar to overfeeding. If they are underfed why the purpling after i raised their food? I use Heavy 16 nutes, they're in 50/50 fox farm/ready gro. They are at 800ppm Truncheon and in week 4 flower.

Found PM. bought sulfer burner and sulfered. Still hasn't gone away. I realize it's systemic however I'm not taking down my rooms. I am looking for advice on a sulfer schedule to manage the problem. I am not sulfering into flower I know it ruins my buds.

Thanks for your input.​