So, I have two human civilizations on different planets. They both start from the stone age. (How the humans got there is not particularly relevant.) It is worth noting that most of the biosphere on these planets is similar to that seen on earth; they have the same domesticatable animals, most of the same predators, e.t.c.
Planet A has developed a level of technical sophistication similar to that seen in 1700's Europe. Rifles are the primary weapons, They have steam engines (and possibly very early locomotives? I'm still unsure on this), And large, sophisticated sailing ships like galleons and caravels. The civilization on planet A has moderately advanced metallurgy, and is able to consistently produce high quality steel; said steel remains fairly expensive, though. All of this said, their medical knowledge is very poor. Plagues abound, Miasma theory of disease is the leading understanding, and a fever often spells death.
Contrast this with Planet B. Planet B is still using swords and crossbows, and any sort of metal is quite valuable. However, they fully understand germ theory, know the difference between bacteria and viruses, and have developed vaccines, alongside a robust understanding of human anatomy. Part of the reason for this is that a small portion of Planet B's population are magic users, who may be able to sense the aura of bacteria or some similar nonsense. Healing mages must also have a good sense of human anatomy to heal injuries, as a poorly applied magic healing can cause cancer due to magically induced cell division. (As a result, Planet B also has at least a basic understanding of cancer treatment.) They have also developed microscopes, and by extension, relatively advanced glasswork and optics.
Both planets have developed agricultural tech, but in different ways; Planet B uses magic to bolster crop yields and allow fallow fields to recover more quickly, while Planet A has developed an industry to collect guano for use as fertilizer.
MY question is: how plausible are these two civilizations (putting aside the plausibility of magic)? Does the technological advancement of Planet A necessitate a higher understanding of medicine? Does the advanced medical knowledge of planet B automatically give cause for a greater level of technological development? Are there any obvious consequences of the technological and magical development that I haven't thought of?
what conditions would cause Planet A's understanding of medical science to stagnate, even as technological advancement continues as normal? Would Planet B's advanced medical science necessarily result in a rapid expansion of technological development?
Edit: It is important to note, of course, that not all of each planet has access to the same technical or magical knowledge. I am referring to the most advanced civilization on each respective planet.