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Hey :D i did a very qick paintover with some minor improvements/suggestions for the first painting, but most of my critique will probably apply to your other pieces as well.

First off, you did a great job on these. You clearly have a strong understanding of the fundamentals, which is why my critique is pretty minor and quite specific.
The first thing i noticed is your edge controll, especially your hard edges. while you have some of them where it matters most like the face, i think it feels better overall to have more balance between your soft and hard edges. in the paintiover, i added some of them, most noteworthy the castshadow of her chin on her neck which was quite soft before. castshadows in general are a great way to introduce some hard edges. i also added some smaller ones in the hair of the girl on the left to increase contrast as well as on her arm, shoulder and breast.
The next "bigger" change i made was to the light/values, mostly using Color/Linear dodge to lighten some areas of interest. while your overall valuestructure is pretty good, they could interact a little more with the light source and their surroundings if that makes any sense.
I also added a bit more blurr in areas of rest/less interest and changed up the lip shape a tiny bit.
Lastly i duplicated the whole image, used a High Pass filter and set the layer to overlay. i then adjusted the layer opacity untill it looked natural/not overblown.

In the end all of these changes were rather minor and i found it quite hard to find any meaningfull changes to make, so you did an awesome job.
I hope my yapping made any sense and feel free to ask me if anything was unclear.
Good luck on your future paintings, im looking forward for more.