Over time, the plant growth nutrients are depleted at varying rates depending on the type of plant and various growth factors. This results in a gradually weakening nutrient solution along with water loss from plant transpiration. My original plan was to conduct a nutrient change at about the two week period and increase the nutrient dosage from 1/2 recommended strength (plants in early growth stage) to full strength.
An experienced hydroponics grower suggested I wait until 3 weeks before changing the solution. His reasoning was that the younger the plants are, the fewer nutrients they require and they may not have used them all in only 2 weeks. He also suggested letting the plants' appearance assist in guiding when to change the nutrients.
I noticed slightly less color in the new leaves on the basil and that triggered my decision to change nutrients over the past couple days. It is right at the 3 week mark, so kudos to my friend's recommendation!! Save a little time, save a little nutrient.
I replaced the solution with clean water and let it "rinse" the system for 24 hours. This is to remove excess salts and unbalanced nutrients from the growing media and roots and allow a fresh base for the next few weeks.
After rinsing for a 24 hour cycle, I replaced the water and added nutrient at full strength this morning. A PH check a couple hours after the nutrient change showed a bit on the alkaline side. I added PH down and brought it to 6.5. Too easy and very little time required.
Now that it is on full nutrients, I am expecting even greater results.