Mixed run/clone

I’d be willing to bet these aren’t gonna have any significant fade.. can’t really pinpoint exactly why but it looks maybe a bit of overfeeding with N in flower. You may get some slight chlorosis late on but I doubt you’ll see anything on these. And as far as the general question- it’s genetics.. I’ve seen it early as hell like week 4 almost.. some hit super late and fast the last week before uou pull. Some not at all.

To really encourage a fade and color change you can also lower your temps as well to between 16 and 17C at night but you'll have to account the RH as well so as not to put your VPD off, if you check out my LA confidentials you'll see some nice purples my temps and Rh are 21C to 42 day time and 17C and 41Rh, looking awesome

Yes, you can get a fade. But you need everything to come together. Some plants will throw fade off. Then again most will wait, or at least the bulk of fade will appear in your ripening. And then some just don't throw any fade. As you get into later stages of flowering you should adjust or try have your lights come on during the hottest part of your day, and off at night. (As I'm assuming that's when it's coldest in at yours) You can let that temp drop as far down as you'd like during ripening. Well 18c..Ish. I've seen it go further. But, that's cold enough for me in any room of my house. Except drying room. But, as I've said. All phenos are dif. I know you running clones. But, did that pheno fade out. If so, just carry into this grow what you did your last. As the aim of clones is to replicate your past results.. And just 1 more thing. Your growing bud to get high. Not to have fancy leafs. So I wouldn't worry about it too much. But, you like what you like. So, Good luck. But, the aim of the game is to get some good bud, so once that's achieved everything afterwards is a bonus. Good Growing