4.5 means two of the boards dropped out, hence you get a third of the hash rate.
Interesting, on the Ant Miner web console, it says all 3 are online, just hashing at 1.5k each... Most folks were reporting they would see HW errors or the 3rd card going to 0 when their overclock was too high, so I was assuming this was slightly different.
Well, in my case I would see 2 hashing at 0. So maybe a slightly different scenarios.