First Grow - 60x60x160

if 12l pots are around 30x30cm , you can fit 4 inside , but not much space after that . But the answer to your question is a bit more complicated , planning to grow just autos ? or photoperiod too? Usually autos don't grow that much and sometimes 4 its quite a lot for 60x60 grow , you can go with 3 and save some space for future dehumidifier . If you grow photoperiod , I suggest just 2 and do LST on them (which I do suggest on autos too)

I guess it is a bit late now that you have started two seeds, but I would have recommended only doing one plant in a 60 x 60 tent. Neither plant will be able to flower directly under the light, as they will have to be off to the sides, which could compromise growth and peak flower quality, but nothing really major, just a bit less than optimum. As it is your first grow, going with one plant would have also given you a chance to fully concentrate and learn from a single source, and although 2 plants may not seem like much, dividing your focus doubles your inflow of information, as both plants will grow differently and have their own unique likes and dislikes. Far better to have one plant and learn as many basic fundamentals as possible, such as watering, nutritional requirements, pH, training and light distances etc. that you can implement into your future grows, however, growing is fun and fairly straight forward, so you should have some success, even if your plants are a bit crowded, but a bit of well thought out tying down of branches can add many benefits. I would suggest you go with 18/6 for your entire grow, this is optimum for both auto flowers and photoperiod plants in vegetative growth. Also be prepared to be patient, whatever is stated by the breeders as maturation times are completely fictional, with most autos taking between 10 and 16 weeks, despite any claims by the breeders. Other tips are, - aim for moist, but not too wet and not too dry substrate, and only water once the first inch or so of the surface has dried out. Deep watering is better than little amounts of water often, however when it comes to feeding, little often is better than strong nutrients periodically. Since you are growing in soil, try and follow a plain water/plain water/feed/plain water/plain water/feed schedule, so your are feeding every 7-10 days, however, Bio Bizz light mix is fairly poor in nutrients, so you may have to up the nutrients or feeding frequency, depending on how your girls develop. Also, there is absolutely no need to cover your plants/seedlings with a plastic bag/mini sweat lodge/humidity dome thingy, nor is it necessary to mist your plants, all these things can lead to mould/fungal problems and cannabis does not need rain forest conditions to grow, but a drier climate is fine. Your plants need good air exchange for proper growth, something that is not available under a cover of any sort. I wish you good luck and much happiness with your new adventure on this journey of cannabis cultivation discovery! Hope this helps,........ Organoman.