In my understanding, the original poster commented only on a pattern he/she observed with minor price margin fluctuation. It is not related to overall decline of the market.  I noticed this pattern as well. Simple example: The price of ETH was holding between 273-270$ all day but RIGHT after 5pm EST it dropped to 262$ for about 10-15 min, then around 520pm everything went to "normal" - 272$. But Honestly i do not understand  why. it is happening.
BTC , LiteCoin do not follow this pattern. I noticed it only with ETH, ECT, which actually make sense why these 2 pairs act differently in regards of pricing pump/dump