If you've used the same amount of water this whole time, see no pests, and the ONLY thing you've changed is the feeding ratio, then I would consider using a flush here. The medium does not look like something with poor drainage, so my first thoughts are that the root system was violated in some way. Overnight like that after a feeding..? Kinda makes sense to me, too. In this instance, if you've got the meters, I would do both a slurry and a run-off reading of pH and EC values. You might need to use something like
Clearex here (it's been YEARS since I've flushed a plant or used anything like
Clearex/FloraKleen, so please, take that to hear when reading my advice and be careful).
If you've got it, I would also get some kind of microbes into that root zone, ASAP. As per usual I'm going to advise Capulator's product, IIRC his foliar pack is what's packed with the most microbes. If you don't have that, but have worm castings, make a tea and use that to flush. But my thoughts are that you've possibly used far too much fertilizer and done some burning of the roots. That, or something's girdled the plant. Maybe take a look at the roots (if no one's said to do that).