Hi,
After looking at your photos and reading your posts I do not think these are pregnant fish. Looks like bloat or dropsy to me, both of which are PAINFUL & NOT CURABLE! I've been around the hobby all my life (my father had many tanks from 400-gallon tanks to 10-gallon tanks, salt, fresh, you name it, he just loved fish. He passed away a few years ago and my sons have taken up the hobby for the last 10-15 years and I have just gained a lot of knowledge that has been around them all this time. I remember my dad teaching my sons about dropsy and bloat and being very, very clear that these conditions are PAINFUL & watching the fish that appears very much to be true. I would euthanize them with a couple of drops of clove oil until they are unconscious and then once they are anesthetized I would add more until they passed-on. I could not allow an animal to continue to suffer that kind of pain.
We lost a beautiful pink swordtail (a pink comet) who came down with dropsy (which from my reading seems -9x out of 10- to be a form of cancer) and just watching her was so upsetting, we had to put her down, I couldn't let her suffer like that.
We stopped breeding guppies simply because they appear to be a big genetic mess. Females who deliver and are literally deformed after the delivery as it bent their spines with the intensity of it, mothers eating the babies if you don't get to them into a breeder fast enough. Yes, they are beautiful fish but I have never had a breed of fish more prone to every problem in the book as guppies (well, maybe black mollies but the black mollies we breed are of the saltwater variety and seem to do much better than their freshwater counterparts). If you are really set on guppies you may want to try breeding a guppy/endler hybrid. They are beautiful fish and it seems to really put a stop to many of the genetic problems you see with guppies in general. We breed endless and on occasion guppy/endler hybrids and have been very happy with some of the beautiful fish we have gotten. Right now I think we may have a new tail shape in a guppy/endler hybrid. He appears to have a 'trident' tail, kind of like 'Neptunes Trident'. I have never seen the like and we are going to see if we can reproduce it. I'll see if I can get some good pictures to share but in the meantime, I would euthanize the fish with bloat/dropsy. It's good to want to save the life of a sick fish but you have to also take into consideration what the fish is going through. Is it right to allow a fish to suffer for weeks while you try to cure a condition when you are not even certain what it is? Just food for thought.
I hope it works out well for you.
Sláinte
Adi