Phosphorus deficiency? PH problems?

Yo @BlaKX , 21°C at night isn’t really cold enough to bring out color from temps alone, so I’d say it’s probably just how that pheno expresses itself. That said, with your pH sitting at 6.0, it could be slowing down phosphorus uptake a bit. I’d try bringing it up to around 6.3–6.5 to make sure she’s still feeding properly. But if it’s only the Mimosa doing this and buds look good, you’re likely all good. She’s probably just fading naturally. Looks like you're close to the finish line!