This is one of my favorite topics.

30 years isn't that long. It's a human generation (and a half), but it's a long weekend to elves, and a hard week to dwarves.

That said, I tend to peg their medical knowledge as about equivalent to their other physical technologies... 14th or 15th centuries. While the gods may have gone (and taken their magic), you're still going to have a couple of big forces that already hoard knowledge, and will leverage that knowledge in the absence of magic... the Churches of Oghma and Gond (and their related churches, Denier, especially). While I don't know if they necessarily have germ theory of disease, I do think they're likely to have a basic understanding of hygiene (esp. handwashing), and know a lot about medicine divorced from magic. I DO think you'd see decline in overall health during this period, but that's partially because healing spells are so hugely efficient. Sure, it may not be HP damage, but spells are going to mend the skin in ways that bandages do not. They're going to prevent cavities in their quest to bring you up to full health. Getting a Cure Light Wounds spell every few months will lead to some fairly effortless health, if your nutrition is decent.

You're also going to see some decline in nutrition, because a lot of farmers likely get a boost from plant-priests using Plant Growth and such. There's still going to be knowledge... they might know the advantages of a three or four field farming system... but it's not going to match up to magically making things right.

As for general technology? Maybe. Lantan is already moving in a technological direction, and there will be a lot of interest in their exports. You may see an increase in power of certain guilds, as their ways of doing things become more necessary. But 30 years isn't very long to build the infrastructure necessary to move towards a high tech society... you're going to have several years where a lot of people are figuring magic will be back any time now, after all.

Where it will get interesting is the societies that rely heavily on magic. Thay is gonna spend most of this time on fire. Halruaa is gonna be a ruin. The Anauroch might get smaller, since it's magically maintained. What's gonna happen to dragons, or undead, or even races like the genasi or aasimar (consider that they're supposed to be prevalent in Mulhorand)?