Sometimes it takes months before shrimp feel "at home."
Totally agree. You may get lucky that new shrimps start breeding right away but most often that's not the case. Because of this, I recommend getting shrimps about 3 months old and when they are matured they are also used to your water. Breeding is much better that way.
That said, I got 10 female bee shrimps from a breeder about a month ago, I then found out 1 may be a male so I separated that guy, 8 out of the other 9 are berried, actually 5 of them got berried within two weeks. But I consider that just luck. They are all new adult though so easier to adopt. Most of the adult shrimps (other than A/S CRS) take at least 2 months before breeding steadily.
If you have grade c males, definately cross back. By back crossing to the parentage that has the original modifiers, you help to solidify the grade c coloration in the strain.
F1s can also be crossed, but will take a longer time due to different modifiers introduced from "higher" grades.
Out of curiosity, how long would it take for the pattern to "stabilize" would you say? If he sold it to us, it would help stabilize the strain right? Since there is more population with the C grades. Together, we will bring back the C grade population!