Air Conditioning - New centrail air install.....have a few q's?

We just had a central air job done. House is about 1800 sq ft, ranch, hw bb heat so the air handler/ flex ductwork is in the attic, 12 seer 3 ton ruud unit, and I have two attic fans set at 90. I had it set to 74 for during the day and 70 at night. During the day it seems the air coming out of the registers is only between 58-62 degrees, but at night the air temp coming out is near 50-51. Does this sound normal? Is this because the ductwork is warm or because the lineset going up into the attic from outside is warmer during the day? It was high eighties up in the attic today which I didnt think was too bad considering it was about 90 today outside. Any way to get the air temp cooler during the day so it will be easier for the system to get the house cooler? It seems like it would be hard to get the house's temp below 73 or so during the day. They said it was charged the right amount, and came back yesterday to double check?

The discharge air temp is all relative to the outdoor temp. In the heat of the day the hotter air going through the condensor removes less heat than at night with the cooler air where it can be much more efficient. This results in exactly what you are seeing.

Ok so are the temps I am seeing normal?

In the heat of the day take a temp reading of the supply and the return. Prefeerably close to the unit as possible. You want about a 15º split.