I used/use two Dyna gro products. Grow and Bloom and every time I've used the bloom formula I'd get a CA/MG deficiency.
In hydro (DWC), city water, RO water didn't matter, I'd get a Cal/Mag deficiency every time when using the bloom during flower. I was a big supporter of dyna gro but I've seen now that the Dyna Gro Bloom is not formulated correctly. Not just for cannabis but for other garden variety vegetables. I grow a great deal of other plants and even my tomatoes would get a bad CA/MG deficiency.
Sure this product is affordable and easy to use but for me, it's absolutely mandatory to have a fresh bottle of Cal Mag on hand if you're going to flower with it. Cal Mag is not cheap either when running even a modest hydro garden. I've since switched GH maxi bloom for evaluation for flowering nutes.