This comment has been deleted by unclescott

It might be possible to add a bit of a liquid children's vitamin mix, very carefully, to flake food. After the vitamins are dry, crumble the flakes up and feed them to the fry. A lot of paste food recipes suggest adding those vitamins when that concoction is cooling. (Heat destroys them.)

Depending upon where you live and your student budget, there are also vitamins sold to be added to a fish tank. I don't know how well fish absorb them. Feed that flake dust from the side of your food container to the fry along with what you are using.

Vitamins tend to spoil or lose their effectiveness in older flake foods. That is why some aquarists will leave their big can of flakes in the freezer and keep a week's worth in a tightly sealed container near the fish. (I try to feed from no more than two cans and finishing them (a regular flake food and a spirulina food) before opening another, even if it is a sample.

This is easier to say than to do, but feeding a variety of flake foods will help. If a few live foods or frozen foods can be added to the mix, so much the better. Adult brine shrimp by the way, are useful, but almost any other frozen or live food is actually better for your fish in that it will have more food value. Killies fed exclusively on brine shrimp (even the newly hatched nauplii) have been known to develop diet deficiencies.

If you have access to live daphnia, which might have been feeding on a number of mineral and vitamin rich foods, they might help. Most aquarists who keep a few fish in a tub in the backyard over the summer are amazed by the color and health of their fish by the end of that time. The assumption is that sun and live food make a huge difference.

Please don't get yourself in trouble, but can you find mosquito egg rafts? (Are you in an area which is currently warm?) Adult mosquitoes and just hatched baby mosquitoes are wonderful food for appropriately sized guppies. I have placed a mosquito egg raft in a fry tank and left for the weekend. As the 75 to 200 baby mosquitoes hatched out (from that one small egg raft which looks like a piece of charcoal scratched out by one's fingernail), the fry grazed on them.

See http://www.lawestvector.org/mosquitobiology.htm

Maybe a little sun on the tank for an hour a day (if it doesn't warm up the tank very much), a chance to nibble at green algae (which I hate in a tank, but I don't make the rules of nature for the fish), as much variety in their diet as you can and even more water changes will also help.

It is remotely possible that the condition is hereditary. The mother could have one gene for lordosis or socliosis which is masked by the other dominant gene. If her mate (a brother?) also carries that gene combination, you could expect trouble and 1/4 of the fry (if it was a simple one gene cause) to develop that condition. There is not much you can do except mix up your breeders to avoid inbreeding.

Another cause of skeletal deformities is fish tuberculosis. Mycobacterium multiply in dirty tanks and cause Mycobacteriosis or fish TB. Greater cleanliness in the aquarium (and the store's tank although there is not too much we can do there) may help prevent this malady.

Hopefully these last two issues are not behind the problems you fry are facing. Try mixing their diet a little more.