TTL IC logic high output doesn't reach high enough voltage
You appear to have some LEDs connected to your outputs. These will limit the voltage to 2(ish) volts if driven direct from the outputs. TTL outputs are not designed to drive LEDs to ground and have a valid logic high level. Their weak drive current is however convenient for driving LEDs like this.

TTL is much better at sinking current than sourcing. If you want to drive a LED, you should connect it to the +ve rail, in series with a current-limiting resistor. Unfortunately, that means it will be 'on' for a low output. This is a small price to pay for driving the LED properly, and delivering valid logic states as well.