I just came across some interesting info, and I think it's rather important...
Never really thought there would be a major difference in products, so I usually get what's on sale. Anyway, I have a couple botles of the stuff around...and was comparing the labels.

All are made by the same company, which is B&G Foods. All 3 are unsulphered. Numbers listed are from the labels, and are for 1 Tablespoon. (not that that matters, it's a percentage)

Bottle 1 is an old bottle with less than one application left in it. It's Brer Rabbit Full Flavor, and the label says:
Calcium - 10%
Magnesium - 20%
Iron - 15%

Bottle 2 is one I'm just finishing, is Grandma's Original, and the labes says:
Calcium - 4%
Magnesium - 2%
Iron - 4%

Bottle 3 was purchased last week, and is Brer Rabbit Full Flavor (same product as before) and it's label says:
Calcium - 8%
Magnesium - 8%
Iron - 2%

I'm guessing it's something to be addressed when dosing your plants, or cracking open a fresh bottle. That's a pretty wide spread. Makes a lot of sense too, with all the different ratio's I've seen thrown around the past couple of years.

The Grandma's page on their site tells of nutritients in the molasses (copper, manganeese, iron, magnesium, potassium, and that it's made from cane sugar. The Brer rabbit page says nothing about nutrition, lists no 'Nutritional Facts' (like on the labels) but does mention to check label for nutrition info. (big dark secret about ingredients, lol)
Grandma's Molasses
Brer Rabbit Molasses

So when you use molasses, pay attention to the labels for concentration (percentages) of the nutrients. These are the two I've been using, (from Walmart) and thought performance or lack thereof was a strain tollerance issue. Perhaps not. Might be a ratio thing.

Perhaps it's the use of plants other than cane sugar that Brer Rabbit is using, and the quality (variability) of the manufacturing process. But jeepers...I just can't see a major manufacturer saying..."It's only off 20%...that's close enough".