yep, JJ is on the money there, you will need to do atleast a little research on growing mmj to really be successful with it, if nothing more than to gain knowledge of possible problems that do occur.
ph level of soil/dirt or hydroponic solution lets you know if it is TOO ACIDIC or TOO ALKALINE, either excess(acidity or alkalinity) will cause what is commonly known as "nutrient lock out"- this is the situation in your grow where the plant can no longer take up any of the nutrients either within the soil itself or nutrients that you may feed it. again, soil that is too acidic or alkaline will prevent your plant from being able to take up ANY nutrients in your soil already or fed to it.. IMPORTANT TO KNOW
other things are kinda vital to get sussed.. watering- how often to water your plant and when to know when it needs more water or not.. this should be basic knowledge for you. a good gauge to know when to water is simply stick your index finger into the soil upto around the middle knuckle or half way... and if the soil feels dry at that level then water, if not then wait until it is... under watering will generally result in the plants leaves drooping down(but not looking sick) and over watering plants can have a detrimental effect too... this is an easy way to gauge when to water. added to this will be feeding schedule- how often to feed your plant and knowing when you have gone too far and have overfed them and will cause their roots to burn.
temperature and humidity(moisture content in the ambient air) are things that will effect your plants growth too.. altho, being outdoors like you mention is harder to control as it is if it were indoors... if excessive humidity or temperature, can stunt your plants, cause a number of issues with your plants development and can be destructive too.
we dont mean to make it sound complicated! this will become second nature and part of your basic checklist of things to consider when you grow.
as far as food is concerned, as mentioned above... it is also good to know and understand nutrients and minerals, elements that are within your plant food... plant require different amounts of different nutrients at various stages of their growth, for e.g. when it is in vegetative stage(before it begins to flower) it uses alot more Nitrogen than it does phosphorous and potassium(N.P.K on most plant foods)- as an e.g. so understanding these things will greatly increase your plants development too.. and hence, greatly improve the size and quality of the buds you harvest at the end of it.
flushing is running water through your soil and letting it run freely out of the bottom of the pot, this aids in flushing out excessive nutrients from the soil- excess can contribute to your soil being too acidic and hence preventing your plant from taking up any nutrients- as mentioned above. simply run water through your soil for a good 10-15 mins atleast... this also has a soothing effect on plants that have suffered "nutrient burn", which can generally be seen in the leaves- turning crispy and drying up, curling up and turning brown, almost as if they were literally burned. dolomite lime is also a good additive to help bring your soil ph down if too acidic.
with a good understanding of these things i am sure you will be mastering growing and harvesting HUGE buds in no time at all!!
well, thats my 2 cents worth! and i hope you are able to get your plant back on track asap!! all the best and
good luck!