What can I do to save them? Slow growth, new growt...

Hi there! Your pH is wrong, should be between 6.0 and 6.5. As an emergency move, I would flush the soil for 2-3 days then repot/transplant her into bigger container with 'fresh' soil and see how it goes. No more nutrients, just plain pH'd water, 6.2. And much love of course! Good luck & Happy growing

Hey there I'd raise that plant light up to around 24 inches or 18. Check the drainage on your pots. Also once they're big enough get em into bigger pots. Also I see you've got grow big in your line up if you could add in the tiger bloom by foxfarm it's a micronutrient and will help a lot of problems. But of course ph is good to check too but mines at 6.8 and I'm soil and haven't had that many problems yet. Best of luck....please if anything raise your lights 8 in is awfully close for a young plant like that with LEDs they're so unpredictable.

Along with you overwatering which can stunt the growth, double check your water pH as 6.8 is the high side for using soil. If you can drop it a bit, maybe 6.5.. it will be easier for your plant to consume. Also nutrients at week 2 , too much too soon.. I’d stop until around week 4 or when the plant tells me it needs a dose but for now you have enough in the growing medium without adding any extra so be careful. Less is more and focus on the basics so early on, good light, correct pH water and ventilation and you’ll be off to a great start. Only after when the soil is properly dry too! Good luck

Stop giving them nutrients, they are río young. Also they look over watered; let the soil dry before watering again. Increase the light distance it is too close to the plant at this stage.