Swore I wasn't going to do this....Need help diagnosing. Details in comments.

Sour Apple x Mint Jelly Auto. 6 weeks old total. Starting giving nutes 2 weeks ago, fox farms dirty dozen, 2 waterings with them. First was at 1/2 strength, second was at 3/4. Just water and cal mag between, because I thought it could be a deficiency in one or the other. Temp is 70-75 (but has dropped to around 65-66 at night a few times) and rh is 55-60. Did give epsom a few times throughout veg. Right about 45 DLI. I don't know if these leaves are turning purple because of genetics or temps, or if there's something up with it. Other plant same strain and everything else is perfectly fine. I've researched all I can without some help. Thank you in advance.

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