How much CalMag is too much CalMag? Also, blossom end rot spray?

One of my Blueberry auto girls is experiencing what seems to be a recurring Ca deficiency. Started right around the start of flower, added Botanicare CalMag Plus at between half and a quarter strength to the filtered water PHd to 6.2-6.8 and noticed no new spots on new growth for a couple weeks. We're further into flower now and I've noticed new growth displaying more spots consistent with Ca deficiency. Last two waterings I used CalMag within the label's recommended strength (4mL/gal.)Temps have been low-mid 70s and rH 35-45ish over the last few weeks. 24/0 light, 600w LED. 3 gal fabric pots, seem to want water every 2nd or 3rd day based on how light they are. Soil pH seems to be right at 7, but I dunno how much I trust my instruments.

So, my question is- is it worth it to do an "attack" dose of CalMag over the next couple waterings? IE double label strength 8-10mL per gallon? Is there a better way to alleviate the Ca def? I also have blossom end rot spray concentrate from other gardening pursuits. While I don't know if it's wise to do any sort of folar spray under my light schedule, is there any benefit to applying to areas lower that aren't under intense light? I've seen Ca called immobile and semi mobile, which would seem to point to there being little benefit to new growth by applying to older shaded growth. Is there a better way than CalMag? I would be concerned using any sort of lime for fear of raising the pH too much (unfounded fear?) I think she has about 4-5 weeks left.

What is your Nitrogen source, and how much are you using.

Calcium Nitrate is what we use for our source of both Nitrogen, and Calcium. Its 15.5 -0-0, and 18% Calcium.

Base formula is 4-20-39= out to 19.5-20-39, and we use Epsom Salts for our source of Magnesium, and Sulfur. On an 8 weeks flowering strain when flowered we will give ever increasing small doses of the base formula until week 6. Then in weeks 2.5-4 we give a MPK-0-52-34 boost.
Then weeks 5-6 we give a Epsom Salts boost.
Weeks 7-8 all nutrients are cut in half. We use small amounts of fert every watering. Promix BX is Medium, and.. Hydro Gardens- Chem Gro 4-20-39 is base fert, and added 15.5-0-0 - Calcium Nitrate. Calcium Nitrate is the cure for blossom end rot.

Fox Farms GP and TB for N. Half strength every third water. Your's seems like a good system for the future endevours and prevention is the best medicine, but that doesn't really answer my question- is it possible to easily overdue CalMag at recommended dose or with a single double strength? Is there a better way to remedy Calcium deficiency in progress?