Outdoor Grapefruit but inside, sue me

Measurements we're took on the 2021-02-07. First problem for the lady this week. I didn't knew for sure but now that it's fixed I can confirm it was a calcium problem, getting used to these. She's now healthy and thriving but for that I had to trade the organic part though, not really a problem because I was still planning to use advanced nutrients supplements for the flowering stage, so I guess it was never really meant to be organic. Week breakdown: 2021-02-07: One brown spot. 2021-02-08: I noticed a brown spot forming on a top leaf yesterday and it got worse today. Don't know the cause. Not worried but I'll keep a close eye on this. 2021-02-09: Brown spot stabilized but appeared on another leaf on the same location. I'm planning a foliar spray of Cal-mag solution tonight when the light turns off, so long for the organic part. Foliar feeding: pH: 6.7 - 23°C - 473ppm 2ml/L 2021-02-10: Brown spots are still appearing, foliar feeding didn't seem to do much but I'll wait a bit before doing anything else. I'm not even sure of the problem. 2021-02-11: Brown spots did not got worse at least not a first glance but since it's not going exponential, I'm guessing the foliar feeding actually worked to a certain extent. 2021-02-12: I fed them for the first time this morning with a calmag solution since I'm now pretty sure that it is a calcium problem. 2ml in 1L of water poured over the roots, waiting for results. pH: 6.4 - 23,2°C - 452ppm 2ml/L 2021-02-13: No signs of toxicity and it stopped spreading, great.