No criticism, just great to see folks sharing and learning!
Not saying that it is N deficiency, but light stress appears on the parts of the plant closest to the light - the top. Nitrogen is a mobile nutrient and the plant shuttles it up to the new growth causing the lower leaves to turn pale green/yellow.
So if the chlorosis is at the bottom of the plant, it's not light stress. Since it's at the bottom of the plant, it could be a nitrogen deficiency. However a nitrogen deficiency normally shows chlorosis from the edge of the leaf inward whereas yours seems to be starting at the vein and moving outward. Do the yellowed leaves pull off easily? If they do, that's another sign of nitrogen deficiency. If you see the issue continue to creep up the plant from the bottom towards the top, it's another good indicator of a nitrogen deficiency.
Oftentimes in determining what could be wrong it's just as important to determine what isn't the issue as well.
More info would help...how much water have you been giving and how often? In what size pot? Also, assuming you are in flower since you used Beastie Blooms. Flower is often when problems will show themselves as the plants enter a new stage and needs change as well. Beastie Blooms has 0 nitrogen in it and lots of phosphorous and potassium. Were you growing all organic or with synthetic nutes?
Many issues can be caused by improper environment. Ninety-five percent (okay, I'm making that up, but it seems like 95%!) of problems can be fixed with maintaining the correct environment. Temp, humidity, correct watering regime (super important, especially in soil and even moreso in organic/living soil grows), lighting, ventilation, circulation. I grow organic so I can't say much about pH issues so if you're using synthetic nutrients, defer to those who know more about pH management than I do.
Whatever you do, take a deep breath and wait a couple days. You've done a lot to the plant and it may be stressed...changing lighting, flushing with calmag, adding Beastie Bloomz. If you decide to pursue a particular fix, do it and wait a few days. Does the issue stop? Slow down? Speed up? Change? Then go from there.