Three leaves show this discoloration.

I would say calcium uptake issues, it could just be a problem with ph, or even too much salt in the soil that it's creating a lock out for the nutrients. I had the same problem with my grow. Yes, calcium can be yellowing of the leaves, but it is also browning in spots. It really depends on the situation, because it could be from a number of things, like the lock out, or lack of nutrients, or PH levels being slightly off to prevent nutrient up-take

Going to jump back in here again and say that the folks saying it's a CalMag issue just aren't correct.... a CalMag deficiency would give you yellowing leaves... it's the bronzing that tells me it's most likely phosphorus that's at play. If you see stems that are turning purple, this will be one more indication that you need to increase your phosphorus levels in her feed... Cheers...

Looking like the start of mag issue's . She looks good. Best of luck

Hola, me parece una quemadura por falta de cal-mag, tal vez agregando una pequeña dosis a la dieta pueda ayudar! Buenos humos!👌

This is most likely a phosphorous deficiency.... using some bat guano or bone meal will help... Good luck, mate!