Minor problem (Plants color)

[XP_2600]

Hello all, i am using hylocereus undatus as stock for awhile, and for my environment it seems the best, but some stocks looks paler than others (lighter green) what could cause so ? higher fertilizer or what ? also is it possible to turn back darker (more olive) as i find it more beautiful, thanks.

stock.jpg (96.36 KiB) Viewed 712 times

[hegar]

It looks like the cactus with the "odd color" is also the one, which was grafted to cactus, that does not display the same dark green color the other Hylocereus-grafted cacti show. That may be, why it shows a bit of a stress coloration.

Harald