It is not uncommon for plants under LED to require additional Calcium and Magnesium.
I believe it is an effect of LIebig's Law of the Minimum. Adding higher quality light or more light increased the demand for Mg (and possibly Ca). Mg became the limiting factor.
Cal Mag is Calcium and Magnesium. You have used a heavy dose of Cal Mag and I am not completely sure how the filter works or if it works but I can tell you adding the epsom salt in addition may not be such a great idea. Now you are adding a fix to another fix. This is how you can lock out other nutrients from being taken up into the plant. Too much of any one nutrient is not a good idea.
yeah you are fine only reason to drive LEDS into the 80s temp wise is to drive transpiration. You have to think what manifests as a mag deficiency can be a result of excess Potash. Can we get a picture
With LED lights you need a ppfd/par meter to see how much light is on your canopy I've learned that plants under LED have a full spectrum which intern makes the plants eat more. So all and all you probably have starving plants versus nutrition deficiency got to a higher ec. To see if that work but more than likely they are hungry for balanced nutrition.
Are you only doing hydroton and Rockwool
When the plants are small like they are they do not really up take that much food or water. During the stage you are at it is important to get some dry back in the rockwool. Basically the rockwool is pretty wet and the roots need some oxygen and dry back. If you can lower the watering so the rockwool dries back it will help the plant. Right now the plant is not really doing much as far as root development because it is getting everything and more brought right to the roots so they will stay small if you do not get the rock wool to dry out.
