If you want good cannabis, you must feed them well. Twice a week my plants get fed with liquid fertilizer. Though I had no idea if it was enough, all I can do is follow the bottles instructions and judge by the quality of finished product. Or if I overfeed them nutrients they get something called "nute burn" meaning the leaves change colors showing stress from too much of one or another nutrients.
I will test the PH of the soil, along with the NPK. Nitrogen (N) / Phosphorus (P) / Potassium (K).
For the PH test it is quite easy, just put a tiny bit of soil at the bottom of the vial.
I selected a little bit from each of the four planters.
For this test I did not take out much. But for the nutrient test I will collect more soil.
Filling up the soil to the required level I then add water.
My lab for testing and seed tray production... haha very high tech.
After adding the water to the PH test kit I shake it up and wait a few minutes.
Soon we will know if the soil is too much to one end of the other. Which can cause nutrient lockout. Meaning even if I feed my plants all the needed fertilizer, if the PH is off too much the plants cannot absorb it. So its very important to have the PH within a certain range.
I dip the test strips in the soil water mix and wait a minute.
Wiping off the dirt we can now compare to the reference chart on the bottle the test strips came in. Looks like to me that is around the 6.75 level.. maybe even 6.5 being a little lighter green. Perfect it should be between 6 and 7.
Next we read the directions for the nutrient test, its a little more in depth but I think we can get through this.
Basically we make a water solution soaked in the dirt again. But this time we let the dirt and sediment fall to the bottom so it does not affect the coloring too much of the next tests.
More dirt is collected, I was very careful not to damage roots when taking my samples.
From four planters each gave me around 2 oz of dirt from each. Giving me a cup of soil to test.
Next we soak the dirt in water for a few hours.
We must wait for the dirt to fall to the bottom.
I was expecting to have some nutrient issues, so I bought some slow release fertilizer to help balance out if they need it. Though first I will test and see if they indeed even need more nutrients. If they do adding this Marine Cuisine will help along with dolomite lime to help balance out the acidity the slow release fertilizer will add.
Checking back a few hours later the water has mostly settled. Now I have to take some liquid without getting much dirt in it.
I retest the PH, this one does not require me to be careful with soil being added. It actually suggests I do. But the other three NPK tests will be more clear. Looks like my PH is around 6 so again right where it should be. Glad my well water is sufficient for their waterings. My other home has a more acidic well and may need that dolomite lime if I ever started using it for watering.
After carefully adding soil water to each I then break open these capsules which change the color for each chemical depending on its parts per million in the water.
The results:
Nitrogen is in surplus, I had to look up why this may be. My research shows its normal right now for my flowering plants. If they were in veg, growing leaves and not buds more nitrogen would be used. But very little is needed during the flowering cycle.
Phosphorus is more important during flowering along with potassium. Looks like it is adequate to sufficient.
The potash or potassium looks to be adequate to sufficient.
And finally the PH looks like its around 6.
The plants:
Well it would seem the soil is quite nutritious, and they should be happy plants. Getting everything they need is key to good cannabis.
By the looks of it they are doing great, but the tests help me know for sure even better.
Really curious if I test again during their vegetative growing state they will be using more nitrogen and less potassium and phosphorus. Looking forward to testing them.
Also planning on testing my fields soil and my pond so more lab results on the way.
Tagging 
Having a lot of fun growing in Virginia, its only been legal a few years with home grow here and glad I get to enjoy in the fun.