help please!

My plants haven't shown much upward growth in the past 1 1/2 weeks, the leaves edges started to curl over and they're loosing color. I think the plants are old and need to be flowered. They were stunted by a fungus and it took a long time for them to start to really grow so even though they look small and young they're fairly old ladies. The lower leaves look much healthier than the upper ones also and I switched to a 150w hps a week ago. Any input or suggestions would be great, thanks.

first two pics are from today, second are from a 2 weeks ago

what is your pH?

ph is good i keep it between 5-6

I'm only putting in 1 1/2 tbsp of nutrients and the EC meter is reading almost 2500 ppm where it should be closer to 1800 (says on bottle) I'm using distilled water which reads at 9-10 ppm and i put some root booster in which didn't effect the levels much at all. I don't want to use less nutrients to lower the ppm...maybe not using enough?