The absence of a feedback loop in pH dosers means they cannot make real-time adjustments based on the actual pH levels in the system. This can result in the doser adding too much or too little pH-adjusting solution, causing pH levels to swing too high or too low. Such fluctuations can stress plants, lead to nutrient lockout, and impair plant growth and health. Continuous monitoring and real-time adjustments provided by pH controllers help avoid these issues.