But using tap i shouldn't have an issue with that, right?
Well you say the tap water is only 50 PPM after adding the pH down. So it's not bringing a lot to the party.
I asked about LED because your calcium to magnesium ratio needs to be more like 1:1 with LED lighting. With HID it's more like 2:1 to 3:1.
Too much potassium can lockout calcium.
Calcium issues can be tied to issues with transpiration as well. Make sure the humidity / airflow are proper.
1 mL per gallon of Calimagic will provide an elemental PPM of 13 calcium and 4 magnesium
I think your calcium levels total should be around 180 ish and the magnesium somewhere around 60 (elemental PPM).
Your adding 2.45 mL per gallon of calmag (not sure what brand) and with only 50 PPM of no telling what in the tap water I think you are low on calcium. With calimagic, assuming other bottles aren't bringing any calcium, and assuming that all 50 PPM of the tap water is calcium, 10 mL of calimagic would bring 130 PPM of calcium (180 with the 50 tap) and 40 PPM of magnesium.
You may wanna play with this calculator sometime