emmpey, when you say "I wait...before every third watering", what do you mean "third watering"? You water them in between the drooping? Or you feed them every 3rd watering?

I thought I had over-watered them - I should only really be watering every 3-4 days right? Soil seems quite soggy if I do more than that. Also, should I be adding "nutes" for every watering?

Yes, someone told me that I could have the envirolite close to the plants but when I saw the yellowing, I wanted to rule the lights out as a cause. Thanks for clarifying this for me.

Where can I get epsom salts? A regular store? Do I apply the salts to the water?

I bought a x30 pen microscope. Is it worth me trying to take a photo of the 4th/5th/6th node and perhaps people on here could help me out? How many weeks, considering I am at week 5, will it take before I should be able to confidently determine sex?

And how many weeks away, roughly, would you say I am from changing to 12/12 photoperiod?

With that in mind, am I right in thinking that I should switch to a red-spectrum envirolite for flowering?

L3G10N - the leaf tips are curled a little, and seem quite dry, but are not browning right enough. I'll try halfing the nutrients and see if the yellowing clears.

So many questions!! Thanks everyone. REALLY appreciate it.
Regards
Chester