Swollen Eyes - Probably RI

I got 2 baby turtles around 4 weeks ago and then i got another 6 baby turtles about 2 weeks ago.

A few days ago i noticed that 2 of them had swollen eyes, one of them could hardly open its eyes while the other couldn't open it at all.

After doing some research, i checked to see their swimming behavior to see if they have RI, and indeed i found that one of them was swimming while looping from one side to the other which is an indication that it has got RI.

So i quarantined those 2 turtles in a separate dry container and kept it in the sun while making sure there was a shaded part(since i don't have a heater so i couldn't think of another way to keep them warm, i'm not sure whether keeping them in a totally dry area is safe to do and for how long could be done which is one question).

A day later, i found that another turtle is starting to get inactive and is also having difficulty opening its eyes so i quarantined it with the other 2.

Another day, i found that yet another two are having the same symptoms and i isolated them too.

Today, i took them to a vet and he told me that what they has was due to bacterial infection which affected their respiratory system and he told me to dissolve a capsule of Tetracid in a liter of water and fill the tank from this water and they should be fine in 4 days.

After doing some searching, i couldn't find anyone who used that method which seems to be a pretty simple method, though i wonder whether it is effective.

Any feedback would be appreciated.