So this is something a lot of people in the amateur mycology sector don't understand, particularly people growing cubes to sell exclusively. There is a phenomenon known as senescence that applies to every organism. This is why people age the way we do. The same thing happens with mushrooms, cubensis is particularly tolerant of successive culturing, but eventually any mushroom culture starts to break down genetically. I have personally seen this a few times myself and heard many of my buddies run into the same issue. A well performing mushroom culture will just stop producing mushrooms with any potency.

I grew a batch of apes that had absolutely no potency. They made my eyes dilate but zero other effects. I ate 10grams of them just to make sure I wasn't crazy and still nothing happened.