From my recollection at looking at historical silver charts earlier this year, doesn't silver spot usually pick up in the later part of the year anyway? If so, this slow assent this and in upcoming months is not uncommon.
For me, the fact that the US Mint hasn't raised it's silver prices since spot was close to $20 means it's simply a good time to make some last hour silver purchases before the US Mint does probably bring silver product prices up.
I'll be picking up a few extra ATB 5 ounce coins from the US Mint.