The setup is looking good, and that plant looks nice and healthy, but I think you need to consider some sort of airflow now. Ideally, a desk fan blowing on the plant, and an extractor fan venting the hot air from the top of the room., but even if it's just a couple of PC fans connected to a 12 volt adapter, it will be better than no air movement at all.
For your nutrient question, when to start using them will depend on what compost you are using, and how long it feeds for (which it should say on the pack somewhere), You usually won't need to use nutes in veg if you pot up every few weeks into fresh compost, since it will provide the nutes needed whilst the current pot is filling out with roots. If your soil is very lightly nuted, and your plants start showing deficiencies between pot ups, a half strength grow feed is usually enough to get them through to the next transplant.
Once you hit flowering, use the
biobizz feeding schedule as a guide, although different strains very in their nutrient needs, so you may have to adjust feeds if your plants start showing any problems. With that said, the biobizz feeding schedule usually works just fine for me. I use the allmix feed instructions (although I am using standard multipurpose compost), and i don't use topmax, just grow and bloom.
