I'm sorry for the delay.By floppys, I'm assuming you mean Floppy Rabbit Syndrome (FRS). FRS is a relatively recent occurrence in rabbits, and research on the cause is not complete. However, I'm sure you've read that vitamin E deficiency is the strongest link so far. The mechanism seems to be that selenium deficiency is the underlying problem. this can be the result of foods that don't contain enough (especially when older rabbits are affected), but is most likely that younger affected rabbits are born with a metabolic defect that makes their bodies inefficient at processing selenium. Vitamin E supplementation seems to make up for the problem, allowing the rabbit to utilize selenium.
I see a few potential problems with Richtasol AD3EC. It has been found that rabbits need 40 mgs. of vitamin E per day to help with FRS. To get that, you would need to use 1.5 ml. of the Richtasol AD3EC. Even at only 1 ml., you are risking potential effects from the other vitamins. The amount of vitamin A in the product is huge, and is geared more toward large livestock. Too much can cause liver disease and other health problems. Excessive vitamin D3 has been linked to kidney failure, and in some cases, neurological problems. The vitamin C in itself isn't toxic, but 100 mg. is a large dose for a rabbit. When too much C is given, it leads to diarrhea, and as you know, digestive problems in rabbits quickly become serious.
It would be better to give the vitamin E by itself. You may be able to find an injectable vitamin E at a feed store, from a vet, or online. You would use enough to give the rabbits 40 mgs. per day. Here's a website where you can read more about the history of FRS, and the results of various treatments:http://happyhoppers.forumotion.co.uk/t46-floppy-rabbit-syndrome
After you read the various solutions, you'll have to make your own decision about what to do. If you decide to use the Richtasol AD3EC, I would watch very carefully for potential side effects of the other vitamins. I wish you success in treating FRS in your rabbits.
(The above answer is intended for informational purposes only. If your pet is ill, you should consult a veterinarian. If you find my answer helpful, please click on the green ACCEPT button. Thank you.)