Marijuana auto flower size

A question from a fellow grower:

I started my auto flowers ww and they are all 20 day old today and they
all are showing sex . So my ? Is all three are different sizes biggest
is 6" the next is 4" and the other is 3". So I noticed my ph was
different in all of the the bigg one at 7.2 next 6.8 next is 6.5 so my ?
Is are they on track or should if fix something any help would greatly
be appreciate to. I use the fox farm nutes they seem to do great and a
400 watt power diggetel and it takes my and his and that’s what I’m
running is the hips at 400 watts for 18 on so any help mybe I’m om trade
not sure frist grow so thank u guys very much happy growing

You could be on track, and yes, the differences in each plant’s container, pH as well as other factors will contribute to differences in the way each plant grows and develops.