yellow leaves and spots

I have started these in a nfl system and am into the second week. My ph is 5.6 and i have not added any nutes to the water yet, they seem to have gone yellow over the last 2-3 days. I have a 600w sodium light and am on 18/6 lights. the water is pumped on 18/6 as well. Can anyone give me any advice on the cause and solution to these little mites that might help them improve.

thanx jo

 

Maybee its time to add some nutes.

 

well i added some nutes at half strength and i cant believe how much they shot up overnight and they look a little better today. Thanks for the advice

 

just thought i would update you on how they look now they have had some nutes.......... cant believe the difference a feed makes.

 

Your older leaves that have recovered are showing a magnesium problem. Most fertilizers don't have magnesium. Magnesium sulfate you can buy at the pharmacy. Epsom salts is the other name for it. Apply foliarly at a 2 to 3% solution every 5 or 6 days.... Makes a big difference. enjoy.