3 Week Plants Yellowing

Hi i have a 24 plant setup on a multiflow hydroponic system. I am using Hydroton,and Flora-nova as fertalizer. When i transplanted the clones they were about 10". The ppm was at 1500. I saw that the bigger leaves started to turn a little yellow. I was told to flush them one by one, once i did that the ppm was reading 800 and i dropped it down with water to 670. Its been about a week now and im not sure if im over feeding or underfeeding the plant. Can someone please help me get back on track.

Thank U.

Do you mean your 3 weeks into bloom?
and how did you have clones with 1500 ppm? they shouldn't have any nutes

No the plants are not blooming. I received the clones about 10" tall but im not sure how old they are. I've had dem for about 2 weeks already. The first time i fed them i gave them 1500ppm at 6.3 ph. Shortly after doing this was when they started turning yellow. Im not sure if i fed them too early or most likely over fed them. My initial reaction was to flush them one by one. Now i am giving them 670ppm and the ph is still at 6.3. I did this about a week ago. The plants havent gotten worst but they havent bettered. The new leaves growing on the bottom out of the stems are green but the older leaves on the top are still a bit yellow, the edges arent burned just the leaves a bit on the yellowish side

Oh ok,
yeah you put them into major shock with that 1500, and 670 is still too much
to try and recover, flush them with 5.8 until there clean. water them with just water @ 5.8 for two days
then restart feeding, at 400ppm @5.8 increase by 100 every few days to a week.

this should help them regain their strength