Sorry budy got busy,week in a half old,coco,sensi coco a and b light every other feeding and cal mag on days I dont about every 2 days.this is the only one doidoing it out of ten and one slight nute burn.so I am stumped,its a brownish kinda rusty look,there was the big blotch and then this little dot showed up.I had some temp problems ,and pH with the coco most likely,just seeing if anyone has had it and knows what it is.I appreciate it man!