fim'ing isn't a real thing. either you take a single (or more) node off or you do not. any auxiliary bud below will get increased growth hormone in the ensuing days. if you only clip the leaves, it doesn't do anything. at best, you are trying to clip a node and save 1/2 day maybe 1 day for the time to grow out slightly from that new node, but more likely slicing into a node and slowing it down. Regardless, you cannot make more auxiliary buds than what exists on the plant by cutting in a magical spot. it's just lazy topping, not "fiming"
Get the pH under control, first. then, give it even more time to recover. If the spots have stopped spreading, it's likely healing. you pretty much made it 99% certain what the cause is. so, don't dump stuff into it to try to fix a "deficiency" or something.