Small yellow spot

Small random markings like that is usually just damage from moving the plant around/training. Either that or water/nutrient mix left on the leaves and light hitting it. That's my guess. If the damage isn't appearing elsewhere then it's probably nothing to worry about.

Understand that if you don't see any obvious causes (bugs) then don't freak out. It's probably nothing to worry about. If that symptom spreads then seek answers. You will wear yourself out chasing every single leaf spot. Most of the time the plant will heal itself or outgrow the small things. With all honesty, if you start changing things based on that (and it isn't a slam dunk issue then you may overstress or damage the plant) you will only lose sleep and

money . . . Be calm and grow on

Using the coco loco, did you add any cal-mag after/before you transplanted?

I'm thinking either Calcium, PH or the heater/fan are blowing too close to the leaves.

Could be a few things.

What strain?

Have you been giving nutes, and what kind?

What soil are you in?

What light and how far away?

Do you have a fan or heater near that plant?