That being said my guess is you have PH lockout. In hydro you need to keep your PH range between 5.5 and 6.1 where as with soil you need to keep your PH between the range of 6.3 and 6.8. If you are using tap water, chances are you have not been off gassing it to remover the Chlorine in the water, which most cities and towns add to their tap water. Chlorine is harmful to your plant and should be off gassed before being used.There are a couple of ways to off gas the chlorine, one is to let it sit for 24 hours in an open bucket to allow it to off gas or you can add air stones in the bucket to speed up the process and be done in about 3 to 4 hours depending on how much air you are pumping through your stones. Your local tap water could be just about any PH level I know in my town our tap water PH range is right around 6.8 though depending on where your water comes from it could be higher or lower. Another bad chemical that some places are adding to our tap waters is Chloramine which unfortunately can not be off gassed, that can only be remover through filtration as far as I am aware.They're in a one gallon bucket and the light is 2.5 ft away. I have no idea what the pH is and i don't have a kit.
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https://www.420magazine.com/gallery/data/500/Nutrient_Chart2.gif (Click on this link to see what nutrients are absorbed/taken up by cannabis at what ranges)
If your PH is to high or too low then the nutrients will not be taken up by the plant no matter how much Cal/mag or Nitrogen you add to the water.
I know they sell PH pens on line fairly cheap, some as low as under $20 I bought mine through my local grow shop and paid like $42 as I recall for mine. I suggest you invest in one, while you could use a PH test kit which costs like $5 at your local pet store, they are not very accurate, though they are better then nothing. Another useful tool is a PPM meter, though if you do not sway from the manufactures recommendations to much you can get by without one for a while though when small like what you have, I call them in the seedling stage, I cut their recommended feeding by 1/4 for a couple of weeks then bump it up to 1/2 for a week or two before I go full strength.
Hopefully this has been helpful
