You bought the High Density Photo Black rather than regular Photo Black. The new HD PK you bought is much darker due to extremely high density of carbon and is also much more glossy. We have a limited amount of the previous PK is different sizes.
We also now have an Ultra High Density Matte Black that is more expensive than Epson new black but also 1/3 stop darker than Epson's. The type of carbon it is produced with is exceedingly expensive and too expensive for Epson to make ink with.
Many of our customers are upgrading their printers to our darker dMax blacks and ending up with systems that are darker than the newest Epson SureColor HD system.
The new HD PK fits into regular ICC profiles - but the new Ultra HD MK will require custom ICC profiling.