I cannot see even the slightest bit of yellowing on even one leaf,whatever your doing keep doing it mate because those plants are very healthy looking,they have bushed out really well in a very short time.
All you have to hope for now is that they are definitely females,i really hope they are.
If they are females are you gonna make some clones or continue to grow from seed?
Anyway i will keep dropping in to have a look as im looking forward to your review on the blue mystic if its a female,i only ever had 2 blueberry seeds in my time and they were both male,i did let the pollen spread onto my females though,but i would like to fertilize a proper blue female with one of my own hybrid males,so i wanna know what you think of the blue mystic because there so much cheaper from nirvana than buying original blueberry.
Peace props to your growing skills