Yellowing of bottom leaves at young age

What is your experience level? First timer

Your Equipment:
.1) Type and wattage of lights. (MH, HPS, CFL's, tube fluorescents, LED's) Incandescent 60 Watt plant light
.2) Distance from tops? 8-10 inches
.3) Reflector type? (cool tube set-up, bat wing, enclosed reflector, bare bulb...) Bare bulb
.4) Is there a consistent fresh air supply? Yes
.5) Do you have an exhaust fan and a circulation fan? Just circulation
.6) What are the bulb wattages, kelvin ratings, and schedule? 60 Watt, 18 hour schedule

Your medium:
.7) Specific brand and type of soil, (coco, peat based soilless...) and anything you've added to it. (vermiculite, perlite, worm castings...) Basic potting soil, problem started before adding anything, but then added Nitro rich fert upon seeing the problem
.8) Size of container. Medium, they are young plants
.9) Did you use peat pucks (or similar) to root clones or germinate seedlings? Uh...

Your nutrients and water:
10) Source of water? (tap, bottled or filtered) What's it's ph before adjusting? No PH checking, source of water is faucet then set out under the light
11) Method of checking water ph. (ph pen, test strips, aquarium test kit...) None
12) Method of adjusting water ph. (phosphoric acid, white vinegar, hydrated lime, PH Up...)
13) Specific brand and N-P-K ratio for each bottle. List dosages (quantity per gallon) and current feeding schedule. NPK - 24:8:16, Half a teaspoon/gallon, Vigoro, Everytime watered, only been fed once
14) How often are you watering between feedings, and how much per watering? Every 3 days watered, overwatered at the beginning
15) Any additives or tea's? (Superthrive, CalMag, molasses, Mother's Earth...) No
16) Are your ph levels stable, or do they fluctuate? Dunno
17) What is your ingoing water's ph? ...your runoff ph? Dunno... really need to get some PH strips apparently
18) Do you foliar feed? If so, with what, how often, and at what time do you spray? No

Your growroom:
19) Indoors or outdoors? Indoor
20) What size of closet, room or hut? Big enough for how big the plants are...
21) What are the temps and humidity levels while lights are on? ...With lights off? Temp with lights on - 78, lights off - 72, humidity is betwen 30-40% always
22) Have you seen signs of insects in the growroom? No

Your strain:
No idea... found in the bag
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Sorry the pictures are crappy, let me describe them:
The lower leaves have gone yellow towards the edge of the leaf, now with some brown also... Upper leaves are fine.

Totally new to this stuff, sorry if some of these questions are answered elsewhere. Thought maybe the problem was from lack of nutrients but upon adding the fertilizer, there has been no change. Looking for any advice,
~MaddieJane