Your uplink (*to* the 4926) ports need to be changed to changed to 'tagall' on the end user switches then the other VLANS assigned to the port. This presents all VLANS available on the 'Core' 4926 to both ends of a link.
Since you have four floors, each with a separate link, you do not use an MLT. MLT is for a trunk between two devices, not four devices connecting into one. A single tagall port on each user switch and the four existing ports individually being tagged already on the 4926 takes care of the layer-2 communications.
The ports 20-26 on the 4926 are already set for tagall, that's good. The uplinks on the other floors need to be set that way as well.
Don't forget your core (100.1) needs to have routes pointing backwards to the five networks on the 4926.
TankII