What causes fire to look like dissolved spots? I don't know what setting causes my fire to look like this:

Seems random to me, since I constantly tweak different settings and when I come back to the same settings that give me this result, all of a sudden it works. I'm not sure if I'm accidentally messing something up. Here are the fire sim settings:
Guess the thing with this is that if you put Reaction Speed at &gt;= 1, it'll behave this way. I don't know why, but it seems that way.