Stain in plywood around base of toilet, especially front

Getting a new bathroom and noticed on installation a wet ring all around the base of the toilet, it was lifted and refitted after two weeks and I noticed two symmetrical dark patches on sub floor where it had been sitting, almost like handprints (couldn't touch to see if felt wet). It dries and only sometimes reappeared, not obvious recurring direct after flushing but more when go in bathroom, wonder what could cause, could see no probs with toilet when lifted inside or underneath, has now been refitted on a different kind of triple ply instead of the old double ply and wondering if this will just conceal problem and soak slower?