Current temps and humidity?...if not two different phenos..is the one on the right a younger leaf?

What they said and if they are big fan leaves you will see some fade heading into week 5 if they were old leaves that didn't drop early on.

That is a neat pic of those leaves. Just look how different they are but still a little the same. I would say 2 different phenos.

The were cut from the same mother plant at the same time & fed the same amount of nutes at the same time. They are definitely the same pheno. Both leaves are bigger fan leaves taken from the middle portion of the plants.

Day temps approx 25-28C
Night temps 19-20C
Day humidity approx 30 rh%
Night Humidity approx 60 rh%.

It looks like an early sign of Nitrogen def if so its ok as C99 is a 7-8 week strain so Id expect yellowing early but ive heard Magnesium def sets in week 5 just need confirmation.