Your soil has organic nutes in it? Adding more nutes, even organics will cause toxicity in these types of soil. Most high quality (expensive) soils are of this type. Premature addition of nutes will definitely cause problems quickly. This causes lockout. The plant can't uptake nutes. Adding more will kill it. A good soil will feed a MJ plant for about 6-8 weeks with no additional feed and a simple compost tea should be almost enough to make it all the way.
Your soil is probably way overferted by now, these type of soils are difficult to flush. Put the pot in the bathtub on a crate or something to elevate it. Add three gallons water per gallon of soil. Obviously it won't take it all at once, so take your time. The last gallon or so should have the proper Ph. Around 6.5 or so. Yes, you have to buy a meter, about $40-80 for a decent one. Go the extra bucks for the waterproof model. You will drop that fucker in a bucket sooner or later. You may get lucky and your tap water is in the correct range. Doubt it though. If you can't get the meter immediately, don't sweat it, flush that bitch anyway and let it drain for an hour or so.
After the flush, be careful with the nutes. Start with 25% percent strength, at most, in a week or so. Slowly. over a month or so. ramp up to 50%. Never use nutes at manufacturer recommended levels. It always causes more problems than it's worth. They are trying to sell you more nutes, right?
Organic growing is much more difficult than most other styles. It's a steep learning curve, but well worth it. Search: Subcool. His super soil mix is basically your soil with some readily available additions. It can carry the plant through it's entire life cycle with only water, no additional nutes other than a little compost tea now and then.
Good luck,
Fred