Its not a specific message. I've simply noticed that the third ship in a line, no matter which ship it is, uses up medicine at a significantly greater rate than all other ships combined, regardless of crew size or whether or not we are hauling slaves.
For example. I run a 4 ship line, my 1st, 2nd, and 4th ships all carry about 100-200 medicine at any given time and barely use any of it. My lead ship once made 4 trade trips without using a single medicine. Meanwhile the 3rd ship typically has as much medicine as I can find to buy and shove in it, upwards of 1000 units of the stuff, and it will use like 50-100 medicine per trip. The only times I ever run out of medicine are on the 3rd ship in the line.
Is there something in the code that makes the third ship do this or is it just an anomaly in my save file?