How do i increase the potency?
Increase your horticulture skills. There are no shortcuts. To get the most potency out of a plant you have to give it what it needs. What does it need? What are you doing to it to either stress it out or not provide the proper environment for it to maximize its genetic potential?
If you are having problems with potency off of a known strain, you have a problem in your garden and it is probably the skill of the gardener, and it could be one of many things.
Don't take any of that the wrong way. There is a reason, based upon experience I put it so bluntly.
Search the grow threads on this and other sites. Find one that matches your system (dirt, e&F, nft, buckets, etc.) and is producing crystally digity dank.
Copy that gardener's regime. Do not deviate until after you have a few crops under your belt. Don't forget about temps and humidity. Did I mention to
NOT DEVIATE AND START MAKING SHIT UP ON YOUR OWN.
Not trying to be a dick, just blunt and honest. If you are asking questions like this, your best bet is to copy a successful grow. If you are doing this already, we need a lot more info to provide you with any advice that would be useful.