yellowish color on older leaves

this is my euforia auto, its 4 weeks old, i noticed some yellow spots and full yellow color on cotyledons and older leaves, is it maybe time to use my sensi cal mag max to fix that defiencesy? or what kind of action should i take before my plants goes wasted? last few days it was kinda chilly in the tent ,15-17C moisture is kept about 60-65%. light is hanged at 80cm from the top of the plant, any tips for my plant to go better?

Yellowing cotyledons is normal. Your pots are way to small, could be a root issue?
Anyways with autos you should plant them directly into the pot they will be finishing in(3-5gallon pots are a good choice)