I did a 7 day, 1/2 gallon crock pot sour mash (with raw pilsner) then pitched it into 2 gallons of low gravity, low hopped wort (Berliner). I then left the fermenter in a cooler on a hot pad around 90F for another 7 days. Around day 5 it started forming a nice pecile. When I opened the fermenter on day 7 the pecile looked much different and had spots of brown (see attached). Once I had the wort cooled I pitched 1007.
The gravity dropped from 1.031 to 1.022 during the 7 days of souring. I didn't think lacto would cause the gravity to drop so think I may have picked up some wild yeast. Everything soaked in Starsan before coming into contact with the wort.
FYI, the gravity sample smelled and tasted awesome! just a little sweet.