I have had a betta fish since February with no problems, he lives with 3 African Dwarf Frogs and there are no issues with his tank mates. I went away back to university for 10 days and (did my usual 25-50% water change before I left) when I came back he was hiding in one corner of the tank and not eating, there were no other symptoms so I assumed he wasn't hungry, a week has passed and he has some fin rot, mild pine coning and hasn't eaten anything for over a week. My water parameters are fine I test these weekly I tested them on Monday or Sunday before a water change when I noticed he was looking ill I will post them below. I looked online for fin rot/dropsy symptoms and how to treat this so yesterday (13th JULY) I did over a 50% water change and put in 4ml of Melafix for 7 days as the tank is 37L which is just under 10 gallons, also the heater keeps the tank between 25-30 degrees celsius (this tends to fluctuate depending on room temp but I do turn this down on hot days) I don't have a quarantine tank, unfortunately. I don't have access to various different antibiotics being in the U.K
. such as Maracyn and Macracyn 2 Also, he has a diet of frozen brine shrimp, tropical bug bites, and sometimes pecks at the frog's pellets. I am at a loss as there are no obvious causes for him to have gotten sick any help and any help on how I should further treat him is super appreciated I also ordered some Epsom salt to bathe him if need be. Any help is super appreciated I'm really worried
Also, I will add although he has no appetite when he has to swim he can swim and doesn't appear to be lazing on his side, his eyes are also clear.
Photos: First photo was taken today he seems more swollen but the fin rot has reduced a little, the second photo was taken yesterday after the big water change before using the medicine. I have also added a picture of his tanks if this helps, the water parameters from the weekend.