It's apparent that something is amiss. I just received a mid-1980s Speedmaster back from the watch shop after sending it out for service. It's been worn a few times since, including all day yesterday at the office which was a bit too warmish because of a dodgy heating system and a sunny window. I was just setting it for Daylight Saving Time and noticed the crystal was very slightly cloudy. A close look with a glass finds water droplets collected on the inside of the crystal. Of course I'm sending it back as the work is guaranteed, but what causes this moisture problem and what is suggested to keep this from occurring?
I may seem like Captain Obvious here, but the cause is moisture inside of the watch. Either from the ambient humidity, or perhaps improper handling during the service, now condensing at cooler temperatures. Certainly should not be happening so quickly after a service, so you are right to send it back.
I did a battery change on a mate's Seiko a while ago. He showed me a few days later, CONDENSATION!. Going back through Weatherzone records for my area, the Relative humidity was about 95% during the time I did the watch. I now put any of my opened watches in a container with silica gel bags overnight before putting the caseback on.
Doing a bit of underwater photography myself over the years and taking cameras in and out of the housings you end up with similar problems especially in the tropics. One thing when diving in the hot/humid climate, when opening up the case to changing batteries or sim cards is to try do it in an air-conditioned (therefore) dry space. Getting huge amounts of humidity inside to begin with is bad news, taking it underwater immediately cools the case and glass causing the same problems. one trick for that is to also put a silica pack inside the housing. I have had a watch "fog up" the same way after opening the case back in the humid air, closing it up, getting in the air-conditioned car and instant fog inside the glass. Best to ensure service is done in as much of a climate controlled way as possible. Good idea to send it back. JimInOz's recommendation to use silica gel to dry them out is a good idea also as long as you don't pull it out of the jar into a really humid environment again.
Humid air - this is why my AC goes on in the spring well before the temperatures really call for it - it brings down the humidity... To the OP - were all the seals replaced in the watch? So this would require a new case back seal, new pushers, and a new crown, and possibly a new case tube? Cheers, Al