WQ losing hit points between turns

[Hakko]

Playing as R'lyeh I've summoned Limne the amphibious WQ, and every turn that she is out of the water, her maxHP seems to go down. One turn she went back into the water and, hey presto, her hit points returned. I brought her back on land and her HP went from 72 in turn1 to 22 (t2) to 17 (t3). So I sent her back into the water and her hit points after two turns are still stuck at 17. WTF? She is outside my dominion and she's also my prophet at this point, if that is of use.

I've done a search on this matter to no avail.