Hey smithers,
All very good advice that you're getting from the members above! :clap:
Regarding the leaves - (thanks to TaNg now I know!) your plant is exhibiting something called variegation - it's not a deficiency, just means this is how the leaves will grow, with slight pattern of lighter/darker green on them - as far as I know it does not affect the plant's health in any way, she might just look different that's all. Also I've seen a couple of Auto Ultimates do this before so it's definitely a genetic trait. No need to worry!
If your plant looks sagging and droopy I would definitely back off on the watering a tad and see if that helps. Might be helpful though to know your temperatures and humidity as well, do you have one of those thermometers with hygrometer inside? (sorry if this has been covered I can't find it). A good rule to see if it's over/under watering is to judge the plant - if the leaves are thin looking, wilting and drooping from the stem the plant needs more water, if the leaves on the other hand are firm to touch, and curling down with the stem being firm as well, it means they are overwatered. Both conditions easily fixed!
Be careful about leaving nutrients mixed up for too long - chemical fertilisers (A+B etc) can keep for some time but if you're adding anything else (root stimulators, enzymes, carbs) it can get spoiled pretty fast (happened to me) and the pH might drift and of course it will affect the plant, so well spotted.
Regarding LST there is lots of journals here on how to do it - you might also check out
THIS website - not only for LST but all general info regarding growing (hope it's ok I put this link in here) - there are many techniques explained there and you can take your pick (lst and scrog are recommended for autos, topping, fimming and supercropping not so much).
But most importantly, I think you should give yourself more credit - there is nothing so far in the grow that would warrant the suspicion that it might fail. Yes the tent is small, but many of us grow in small tents and still get decent harvests, it just means you get to be a bit more creative. When the circumstances are different you might want to upgrade to a bigger one. HPS/LED are both viable options, I wouldn't ditch it at all, as long as you can keep your temperatures in the acceptable range (as in not overheat) it should give you plenty of happy buds. Again, later on you might want to upgrade to LED but people have been growing with HPS for decades and it's a good light! So chin up and let that Auto Ultimate show you why it's named like this
:karma Cloud: