I see 2 things:
Your soil- MG is hard to grow cannabis with.
Your water- unless you KNOW your tap water is like the worst ever, use it. Distilled water is not good for plants unless you add calmag to it.
Give a heavy watering, to the point of runoff, with plain tap water at pH 7. Most tap water is about pH 7 anyway so if you can't test it, oh well.
Remember that when you are not running by the numbers, you have to keep up with soil chemistry by occasionally flushing your plants and then re-potting them into a SLIGHTLY larger container filled with fresh, unfertilized soil.