
One section of grout staying dark for a long time
I finished this tile floor (the first I've done) about 24 hours ago. I did the grout in three sections, used Mapei Ultracolor FA plus in an off-white. The first two sections dried out pretty quickly, like in the first four hours or so. I put on the last one at about 8 p.m., and by that point it was getting cooler, like in the 60s, and I had the windows open. But here I am the next day and it hasn't dried out.
I did clean the last section with a sponge more than the others because I was worried about haze. But the sponge was very dry and it wasn't an incredibly large amount of additional washing.
There is definitely no moisture coming from below. Subfloor was well-prepped and this is installed over ditra. It's also very clearly happening only in the area where the last batch of grout was applied.
I put a space heater pointing into the room a couple hours ago, but so far no noticeable change. Do I just wait this out? Anything else I should do?