Why'd silver go down? More sellers than buyers.
I know, you know that already, but honestly, it's the only reason that matters. If you need a "reason of the day" for a market move, there will always be plenty waiting for you during and after each and every trading session. Some of them may even sound plausible, but in the end, they are totally worthless except to those who need to place blame elsewhere for a trade decision that went sideways. Note that I'm not saying this describes you, OK? But, as time goes by, I think you'll find that news, reasons, "analysis" and all the other blather spewing from a million or so sources is meaningless when it comes to profitable trading.
Now, all that said, perhaps there was something that just might have been worth considering that could be considered "news". (I like to think of it as a useful piece of the technical analysis puzzle.) At the top in silver a couple weeks ago the bullish consensus was 98%, which is, I believe, the highest bullish reading for any market, EVER. So, you gotta ask yourself, have all the bullish bullets been fired, and are there only sellers left?
Hmmm. Let's see. A huge one day drop doesn't inspire fear but rather the belief that it's a "healthy" correction and a "buying opportunity". The market rallies back to near the high before the break and the bulls congratulate themselves for "staying the course". If this does not sound like a SELLING opportunity to you, well then, you should certainly stay with your bullish opinion. You've got plenty of company.