It seems like my plant has a bit of a calcium defi...

Hey man, you can surely find organic cal mag especially in powder/dry form. If not you've got a bunch of options starting with diatomous earth (it's got micro in it and cool pestcontrol properties !) or crushed egg shells for the calcium. You're so close to harvest so what I would actually do is to use some chelation agents that will help get the micro needed to the plants. You can find bio enzymes or if you want something stronger you can find bio humic and fluvic acid. you can find the acids in the biocanna line, that's all their "boost" is actually. Other bio brands are much the same so look at the ingredients in the flower boosters. Just my best advice brother ! Hope it helps ! 🚀