I just experienced a somewhat similar situation as the OP except with the Zippy Flightmax 5,000 5S1P 20C packs (not the compacts).
On 10/16/12 I ordered 4 of these packs. Their web site indicated these were the last 4 packs available. I purchased them from the US Warehouse for $39.70 each with total shipping of $16.07. I received them in good shape and they were balanced at roughly 28% charge each. All 4 packs weighed within 4 grams of each other with the lowest weight being 609 grams. I have already flown them and am pleased so far with their performance.
On 11/1/12 I saw that they were in stock again and ordered 4 more of the same packs for the same price and shipping. I received them 2 days ago and they were also in good shape and balanced at roughly a 24% charge. They also weighed very close to each other, however, all 4 packs were much heavier with the lightest one weighing 651 grams. I'm thinking "what the heck" so I compared them. They had the same exact labels on all 8 packs yet the most recent 4 packs received were about 1/8" thicker in size and over 40 grams heavier each.
I have no doubt that the newest packs will have good performance but they are definitely heavier and slightly larger than the 1st batch Ireceived just 2 weeks earlier.