Athos answered grow question 2 months ago
You give us almost no information with which to work. But I can list a few things that you might want to check as a new grower.
1. Temperatures: the plants grows very fast when in the correct temperature range 23C to 29C (73F to 84F). But on the other hand if your temperatures fall below that it becomes slower, and if it falls below 15C (59F) it can slow down to a crawl (and yes it includes night temperatures).
2. Over watering. this is a very common mistake. too much water will prevent the roots from taking oxygen and this will make your plants grow REALLY slow, while waiting for the soil to dry up. You mention that you transplanted to a 3gallon pot, you probably soaked the whole pot? There's a reason most start in party cups, because it helps to regulate the water to a level more appropriate for a seedling.
3. Poor soil. Investing in a good soil will go a long way in giving your baby plants a good start.
4. pH. Been in the correct pH range speeds up things a lot. Yours is not bad, but been at 6.5 or 6.8 would be a lot better.
5. Lights too far away. 4 inches although not too stretchy, it does show quite a bit of stem, indicating that it needs more light or needs he light closer.
See how I didn't mention nutrients? I's waaaay down the list; master those basics I mentiones above and then worry about what to feed the plant.