They Are Growing Quite Slow ... Inside Grow... In ...

I agree with all of the above. You need to use a quality soil add more perlite to your soil mix on your next grow to increase oxygen to your root zone. Also you need pots that drain freely you probably have root rot in there. You can try to drill more drainage holes in the bottom and lower sides of the pots with something called a "step drill" which will drill a cleaner hole than a regular drill bit. Let the plants dry out a bit more than usual before you water again. Lastly you have a large day/night temperature swing root growth slows down below 60 degrees. Low temperatures stress out the roots and they can't get the proper proportion of nutrients from the soil. No more than a 10 degree day/night temperature. Good luck

To me your soil doesn't looks like the best around ( I have the feeling it is an heavy soil ) and it's look like a soil that isn't drying fast and it can retain too much water and could makes the roots suffocate. The soil is the 1st thing I've spotted but your plants looks under feed ( pale colour, lake of nitrogen , maybe magnesium deficiency too ) and your values are giving me the confirmation: 0.8 Ec is too low for that stage, to me 1.2/1.4 are the best values at that stage