This makes me sad, so I will try to help. Will start with things that don't make much difference in the potency, curing, time between drying and testing, intensity of the light, what the trics look like, wet or dry trimming, what the buds look like. On to things that might affect potency Type of light start seeds under something other than hps, veg time how long till flip, care and feeding under over watering ect, temperatures too high is bad, in drying too, medium what they grow in or are fed, light timing hours on and off, genetics. Since you cant run a known clone you need to change things up, what you are doing is not working so change it. I myself do almost everything against common advice and have never had this problem except when the genetics are not up to snuff. If each individual plant does not vary in potency it is most likely some fault on your part. This is all from my own experience's and I started when 2 and 4 foot floro's with starter fuses were the norm. Individual experiences my vary and there is all ways an exception.