Ok, the MSA is good and won’t effect other nutes so that leaves 3 possible causes for a Mg def.
1 - not enough in the soil starting out - good possibility
2 - lockout caused by too much potassium - maybe
3 - pH drift which in an organic grow should not happen unless something is added to change it
I don’t see anything you are adding that would affect pH, so we can rule that out. That leaves K overload or inadequate Mg levels.
I also don’t see any signs of Ca issues so you are not even close to causing Mg OD
Looking at what you have in your soil, I would suggest leaving anything that adds potassium out of the mix for the next week, and water her with a Tsp of Epsom Salt each watering for now. This will bring up your Mg levels but not the postassium. Then see if she looks better in a weeks time
Aside from that, she may be a strain that never looks good growing. For 2 years I grew a Pineapple Chunk pheno, and a friend on here grows the same pheno, that was a great smoke but was never happy. She is always a problem child from start to finish, just a contrary bitch that is always upset about something