I,ve never grown Ak but,
Ph sounds to be fine but could come up a bit 6.7 to7.2 is ideal but i wouldn,t worry about it it,s a long way off nutrient lock.
Co2 ppm is fine Keep it as close to 1500 as posable as you probably know.
But don,t use the smaller plants as mothers as you will end up with a load of slow and small clones, as the behaviour of clones is identical of that of the mother.
Personaly i would let it ride as some plants just seem to be slow and no matter what you do they are constantly back.

Good luck
Disco....