I had this when I had over watered the soil, (during vegatative) I just realised I watered on a regular routine like you noticed and not leaving enough time some times for the soil to dry out enough, nowadays I water when I feel they need it, some days they drink more I've noticed, but I repotted in a bigger pot with fresh coco and didn't water for a week to draw out the damp and it seemed to solve the smell problem.. although 6 week later (3 wk into flower) they have a mixture between sweet aroma and a sweaty sock smell.. I guess this is just the long term effect of this problem.. But lift your put up and smell under it and if it stinks it needs a bigger pot with fresh soil and hold back on watering as much