actually, I start them in napkins and transfer into jiffy pots (dollar store) then they go into tree seedling bags I buy on ebay. Air is the key, I've thrown out all my fancy expensive Air Pruning Pots in favor of cheap reusable fabric containers, I've got 1 gal, 2 gal and 3 gallon pots, nothing I grow will get bigger than those 3 gallon pots, you can get plants 12, 15 feet tall in them, as there way more efficient than any other type of pot, the root balls get super thick.
Airflow is key to everything roots, and where you got roots, you get growth. I also use a bit of azomite, (in the napkin) and also in the dirt, a mild mixture of rapid start on day 2 or 3 and a mixture of humic/kelp at day 5 or 7. That's pretty much my regime for seedlings. Start them out on weak light and build it up. If I do use a humid tent, it's best IMO to keep the bottom open so the roots can get fresh air supply, and don't use them past the first few days, if at all. Depends on the relative humidity at the time, but it's fairly humid here in Seattle at all times.
If that light is weak, just put it up close to the plants, and also, if you can supplement outdoor light that might be beneficial, if it's direct sunlight. Either way, you need as much light as you can throw at them, by the looks of it.