The Youtube fish vet, Dr Richmond Loh, used to only answer general questions in youtube comments, but not the ones related to specific cases because he could not diagnose a fish without examining it first. However, recently he started answering questions about specific cases too, on Facebook. So if your fish have some complicated illness that other aquarists can't help you with, you could send him some questions on Facebook and hopefully he might help guide you in your treatment.
Here's his Facebook page: https://www.facebook.com/Aquarium-Fish-Health-with-Fish-Veterinarian-Doctor-Loh-102365694544453/
Here's his Youtube channel: https://www.youtube.com/channel/UCJLoSfDy187XKu0Lml-oepg
Here's his Facebook page: https://www.facebook.com/Aquarium-Fish-Health-with-Fish-Veterinarian-Doctor-Loh-102365694544453/
Here's his Youtube channel: https://www.youtube.com/channel/UCJLoSfDy187XKu0Lml-oepg