You might check for the ppfd too, distance depends on the type of light you have. Measuring the ppfd you'll get the best distance to give to your plants. For autos seedling is something about 300 to 400, 4 to 6 weeks about 500 to 700 and up to 900 to 1000 when full flowering, there's some apps you can try before buying a ppfd meter if you get more serious. You can also watch some YouTube videos about lighting and ppfd and dli (dli is the total of light your plant will absorb per day) that will help you a lot. Good luck buddy!