Please help first time grow diagnosis

Hi, so my clones are on day 15 since I got them (got them fully rooted). I think I may have over watered early on but they have recovered since then. Im using 3 part GH + superthrive.

The plants seem to look good in terms of new growth, but some of the older leaves are looking terrible. What could this be (pics attached)

not all the plants have these kind of leaves, but a few do, and its usually the bottom or older ones.

I was guessing mag deficiency on some of them, but the dark purple on some of the leaves has me stumped.

Your Equipment:
.1) Type and wattage of lights
- MH 1000W
.2) Distance from tops?
- 20 inches
.3) Reflector type? (cool tube set-up, bat wing, enclosed reflector, bare bulb...)
- bat wing
.4) Is there a consistent fresh air supply?
- yes
.5) Do you have an exhaust fan and a circulation fan?
- yes
.6) What are the bulb wattages, kelvin ratings, and schedule?
- 1000W MH, max temp 85 (lights on) lowest 70 (lights off)
- Schedule is: 1day feed, next day nothing, next day water, next day nothing, etc... so... Feed/Nothing/Water/nothing/Feed/nothing/Water/etc.

Your medium:
.7) Specific brand and type of soil, (coco, peat based soilless...) and anything you've added to it. (vermiculite, perlite, worm castings...)
- 50% Botanicare Cocogro, 40% Perlite, 10% promix
.8) Size of container.
- 1 gallon pots


Your nutrients and water:
10) Source of water? (tap, bottled or filtered) What's it's ph before adjusting?
- water comes from drilled well, ph 6.2
11) Method of checking water ph. (ph pen, test strips, aquarium test kit...)
- ph pen + colour test
12) Method of adjusting water ph. (phosphoric acid, white vinegar, hydrated lime, PH Up...)
- ph up and ph down
13) Specific brand and N-P-K ratio for each bottle. List dosages (quantity per gallon) and current feeding schedule.
- 3 part GH
14) How often are you watering between feedings, and how much per watering?
- after feeding, next day is nothing, and the day after is watering (watering in short bursts on each plant (not on the actual plant but on the soil) via a hose wand)
15) Any additives or tea's? (Superthrive, CalMag, molasses, Mother's Earth...)
- half a cap of superthrive
16) Are your ph levels stable, or do they fluctuate?
- ph levels stay between 6.2-6.4
17) What is your ingoing water's ph? ...your runoff ph?
- 6.2ph in going, havent tested runoff
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?
- indoors
20) What size of closet, room or hut?
- 25x27 room
21) What are the temps and humidity levels while lights are on? ...With lights off?
- between 80-85 during lights on (45-60 humidity level) and 70-75 during lights off (60-70 humidity)
22) Have you seen signs of insects in the growroom?
-no

Your strain:
23) What strain are you growing? (Indica dominate or Sativa dom?)
-Master Kush
24) From seeds or clones?
- clones
25) Is this an autoflower strain?
- dont know what that is

20 inches at 1000 watts is too close. move the light up some. try to get 85F temp down below 80 if possible.

Superthrive is dosed by the drop, isn't it? Try less (or none). It's good in tiny amounts when the plant has been stressed or transplanted.

Yes, by the drop. Label says it's vitamins and hormones. Smells like vitamins. Not sure of the benefits.