5 plants in a homemade DWC system

. i found an organic nutrient made for hydrogardens Its the botanicare line. im having a problem with a nutrient build up on my roots that looks like mud covering my roots. i changed the solution and flushed the roots till they were white again. I mixed the nutrient solution well and i have plenty of air tubes oxygenating the water. The plants still seem to be doing fine. there are no signs of nutrient burn except 2 small spots on 1 plant. but other than that they are green and lush! is the build up normal for organic nutrients? this is my first organic grow so any help will be appreciated

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