First Time Grow Auto Northern Lights

Seems like slow amount of new growth for it to be day 22 and look like this. But first time so if anyone has suggestions based off what it looks like I would so appreciate it! :) I know this is kinda rinky dink set up and might seem lazy/cheap, but I work a ton and am not home much, and am on a budget; just trying to see how growing one plant for the first time goes, as I need this for medical use more than anything else. Would really love to be able to get it right with help hopefully! I used Fox and Farm's Happy Frog Potting Soil in 3 gallon fabric pots, and got a Bloomspect Dimmable SL1000, and have it at 50% right now (had it at 20% for the first 2 weeks, 35% the third week, and bumped to 50% starting the fourth week). Do still have a seedling heat mat under it (even though the weather in west NC is warming up, scared to take it off? Should I?) Watering (sometimes tap, sometimes spring or distilled) every other day/once mostly dried out and feeding following the following week by week schedule starting week 3 found in a fox farm auto feed forum (per gallon): 1- pH water only Weeks 1.5- 2.5 I did a 1/2 tsp grow big and 1/2 tsp big bloom per gallon mix. Week 3- flushed with spring water 3.5 - 1 tsp grow big, 1/2 tsp tiger bloom, 1/2 tsp big bloom 4- 1 tsp tiger bloom, 1/2 tsp grow big 4.5- clean ph/ed water to clear out salt build up 5- 2 tsp tiger bloom, 1/2 tsp grow big 5.5- 1 tsp grow big 6- begin flush for final weeks, can flush a week before you see yellowing of fans (leave enough time to get all the salts out before harvest) Any recommendations based on what it's looking like at this point or what I'm following as a feeding plan would be greatly appreciated, new to this but have tried to read up on what seems crucially important to getting a decent yield. But looking at it I feel it's definitely lacking in areas and would to love to fix what I can. Stem is so thin compared to what I see in others by this point. Thanks in advance for any tips!