How to maximize yield in a small space?

I would reduce to just 1 plant and train her low and wide plus make sure that light is as close to the canopy as the plant can handle and that airflow/exchange is as on point as possible, the air exchange would be likely my biggest question in a cupboard grow. As far as nutes, it depends on your medium. If I was in that space I'd ideally like to go organic so that its as self sustaining as possible and simple to top dress. Synthetic? I use either CX or Goliath, but given likelihood we are in different countries, availability is most likely different brands. The environment is far more influential on the outcome than brand of nutes though in my opinion.

Your lights are to faraway leds need to be closer to your plants and what is your true pull watts on your leds please I have found leds need to be loads closer than other lights or slow growing times

I believe nutrients are secondary to light. Provide the optimal amount of light for larger yield. Get a light meter app for your phone. I like the "PPFD Meter" app best. Then read about daily light integral. Here is a site that explains it: https://www.ledtonic.com/blogs/guides/dli-daily-light-integral-chart-understand-your-plants-ppfd-photoperiod-requirements Then you can provide the correct amount of light for how long you have the light on each day.

Reminds me of that time a long term but not living together partner came home, when we did finally move,I went to hers....I cut a big slot out the top of the closet door for extractor and built a frame for extractor and light and threw all the old clothes stored there out 🤣.... angry

oh, and genetics are 50% of that equation... if the genetics don't afford a heavy yield, you can't wave a magic wand of expensive products to change that. size of colas and density are gentics-driven assuming you are already providing nearly as much light per day as it can use. (read up on DLI to understand in a translateable way... apples to apples compaisons)

work backward from end result... how many colas do you want? be systematic about how you get there. use a screen/netting to organize. do it the same way each time and it won't seem complicated at all. this way you don't waste time gowing things you won't use anyway... pruning higher proportion of smaller/younger growth vs older growth. you'll know you can remove plant growth befoe it wastes effort growing out... don't go too crazy.. weigh benefits of good aiflow vs cramming it full to the brim... if you consistently use a good chunk to microbial growth, it's probably not maximizing the space.

High Kelseyheart, You can train your plants. The mainline technique is perfect for a small closet. You can also use a scrog net to avoid that they grow too tall. The pot size and the time that you let them grow before switching to flower mode (lights on 12/12) can also make a big difference in the plants size. The Plagron nutritions are my personal favorite. You can use Plagron Terra Grow, Terra Bloom, Power Roots, Pure Zym, Green Sensation and Sugar Royal. The most beautiful thing is that they sell all these product in 1 starters kit. That should be enough for a few rounds in a small closet. Check their website or just google Plagron Terra Starters Kit. Happy Growing!