heavy downpour diluting my nutrient solution

[Joe Holden]

Dear Ron, I recently built the 11 plant garden & had it operational a week ago. Yesterday there was a heavy downpour diluting my nutrient solution w/ the rain water passing through each of the 2L bottles back to the storage tank. The question is: is there a planter designed to overcome this problem & how will I determine how to adjust the proper concentration of my solution after being diluted by the rain? Thank you if you have something to share on this. Joe Holden