Nutrients and stretching

Hello – after reading your q+a section I’m left a little confused.Could you please confirm Im doing this right. I make a nutrient mixture up and place it in my grow system. I have an auto top up set up for water consumption.( which adds fresh water only to the system.) I measure my concentration regularily with a truncheon, and add nutrients to maintain a fairly constant cf. Every 2 weeks I drain the nutrient solution from my grow system and start a fresh solution. thankyou  
I also have problems with stretching, my temps sit as 28-30c The humidity is fairly low as I need a reasonable amount of air movement to maintain these temps. I keep the cf around 20 and yet i still get stretching. The lights are a good 100-150mm above plants. what do you recomend. thankyou again 
Hello
Nutrient mixing and maintenance is fine. Dumping every 7-14 days is correct. I guess the more often, the better the balance. If you are adding a lot of nutrient concentrate, say 10CF a week, then dump and restart more often.
As for stretching, the primary reasons are light levels too low or too high a transpiration rate.
Low light could be lamps past their best (replace every 12 months or more often) 
To slow the transpiration you can increase the nutrient strength (CF) reduce evaporation from the leaves with less airflow, less heat, more humidity (if applicable) or a combination of these. You would know more about your system and may be able to identify some area where the plants are less than ideal.
Hope that helps
Scott Andrew
Nerang Hydroponic Centre 4/50 Spencer Road Nerang QLD 4211 Australia Phone (07) 5527 4155
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