I PH'd between 6.2 - 6.9
I don't know anything about using molasses for cal-mag. I did water with it at about a rate of 1 tablespoon per gallon once every week and I still had problems with cal-mag.
I topped dressed every 3-4 weeks at a rate of 2 Tbls. per gallon.
I'm not an expert on any of this stuff and I stopped trying to grow this way. But this would be my advice based on getting to a couple of harvests.
A warning first.
When I grew in coco and dry organic amendments I never brewed compost tea like Mr. Canuck does every week. I tried to substitute compost teas with a microbial innoculant like Tribus. That being said, I never got the results that he does and YMMV.
1. In your current situation I fixed the problem by top dressing with dolomite lime(its a source of cal-mag and is a ph buffer). You can top dress at a rate of 2 Tbls per gallon of media but it might be a bit much depending on the size of your container. Just make sure you don't get a caked layer.
2. Top dressing lime in veg worked for me until I got to flower. Given your current setup, I think its going to be really difficult to avoid cal-mag deficiencies without adding a readily available form of cal-mag(the stuff that comes in a bottle). I would start watering with a cal-mag product at a rate of 1-2 mils per gallon once(maybe two times) a week starting 1 week before flower. I never watered and got runoff (just like Mr. Canuck), making it easy to over apply chelated nutrients and burn the plants. But in hindsight I think getting some runoff wouldn't have been a bad thing every once in a while.
It may be advisable to skip the lime. It was never enough to fix my problems so why bother with it.
Here is what my plants looked like in the end. I got 3 ounces but they had a rough life.
Two plants here have been flowering for 2 months. I was surprised to see all the amber trichomes in one of the plants. I harvested the sample from the very top were there was some purpling from my led's. Should I have picked a lower location? I was surprised because I was using a loupe for a...
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