I have started some blockhead seedlings, they were doing quit well but I noticed some deterioration in the pigment of the lower leaves on one of my bigger ones this morning. They are rockwool plugged into promix bx. Ive given them a few 1/4 strength waters at early transplant stage. Then a half strength water now im on my second 1/4 strength flush today before a full strength. I take a 10 ltr jug of store bought water with 300 ppm tds and remove 4 ltrs and replace with 4 liters of distilled then ph ballanc ....add nutes then re adjust ph. Any idea what this is? They are very squat plants with tight nodes an lots of foliage. ...just wondering if I sgould have had them at full strength nutes already.