Welcome to the forums!
I'm very sorry you didn't have the best start to budgie ownership nor the best advices during the short amount of time you have had your feathered companions.
For new owners it's more advisable to start with just one budgie and to give some time to be better acquainted with the species and doing the research in order to provide the best care possible, before starting to add more budgies to the mix.
Knowing how to read and interpret a pet bird's behaviour and their body language is extremely important and this comes with actual real life experience with the species, through close observation and by beginning the bonding process with the pet bird, in this case the budgie.
I'm also sorry the vet you took your Poe to wasn't very knowledgeable and because of it he may lose the toe.
For future reference, it would be best to locate an avian vet specialist for your budgies.
If Poe was indeed injured by BB, then they should have been separated.
Unfortunately, some budgies have more of a vicious and aggressive temperament and when there is a case of constant bullying and pecking, the aggressor should be housed on a separate cage on a permanent basis.
It's never a good idea to add more budgies when there is not harmony in a flock and the environment isn't very inviting. This will only add more stress on a flock scenario and as a response the birds' frame of mind will shift to "alarm and attack mode" and this is not a good thing.
Another important aspect worth of being considered is your budgies genders, this can also have an impact especially when there is an imbalance on the male/female ratio.
If possible, please post photos of your budgies, front shots of the whole beak/cere area taken in natural lighting (no flash from camera).
Depending on their interactions, you may need to separate your budgies in order to ensure their safety and mental/physical health.
Given the situation your Poe was in, with 3 extra birds it's not realistic to think that they won't be needing vet assistance in the long run and for this one needs to have the financial means to cover these expenses.
The more pets a person has, the more expenses there will be.
And this is just not avian vet expenses, but for added foods, and the many toys and accessories replacements needed in a long term basis.
Also take a look at the following links which can be helpful:
Since you are new to budgies, the information found on the articles and stickies will be extremely useful and you will learn a great deal on the best practices to ensure your budgies have a happy and healthy life.
I'm wishing your budgies all the best and hope the flock situation improves.