Whats up with my runoff?

Ok so im like the 4th wk and have been using Advanced Nutriants.(pics are in my signature) I have not flushed till now. I have had some yallowing and was thinking they were not getting enough nutriants. The plants are feed with 1200 ppm and the ph is 5.9-6.3ish. So last night I was mixing up some nutes and had watered two of my plants. Not sure why but I wanted to check the runoff to see what the ppm was. Well I was very shocked to find it was at 2200ppm. I re-calibrated the pen and checked again and still at what I think is way to high. So the plants apear to have nutes at the ready so now I think the yellowing is not from lack of food but from lockout. so I flushed the others with water adjusted to 6.5ph.
So my question is
#1. What should I expect for a ppm in my runoff growing in soil?
#2. Is the runoff a good way to indicate the need to flush?
#3. Can I just go ahead and flush the 2 I watered with nutes yesterday? I dont want to over water.

You need to flush on a regular basis. Personally I do it every other week. If you don't your plants will suffer. As for...
#1. you want it as close as possible to what your putting in.
#2. answered.
#3. Your call, I would flush though.

Sounds like you have nutrient built up in the soil i would flush like previously suggested, i would think your buildup is caused by your low ph, 5.9 is to low for soil so nutrients are not getting absorbed properly, i would keep the ph between 6.2 - 6.8 nutrients get absorbed best in this range for soil. So give a proper flush and wait till the soil drys before feeding again, give 1/4th strength and work up again

Yes you should also have a flushing schedule, just like feeding, and light. I ran into over nute problems before, I made my soil toxic, the run off smelt like sulfur. Anyways the Grape still came out awesome super a+, but I wonder what it could have done. Now I never have any sort of problems like that. My nugs smell and taste like fruits and berrys, and are never harsh, like my first crops. I would have kept that momma plant, but I screwed her up, no way she would have survived a reveg. She was wonderfull

Ok it sounds like I need to flush the 2 that I didnt do yesterday. Should I flush till my runoff is at like 900 or so? If so I may want to flush them all some more.

flush till its completely clear, than let it dry. I flushed about 30 gallons threw a plant with out over watering. Make sure shes ready for a drink and flush, throw a heater by the container to speed up the time.