Hot Water Loop Balancing

Uneven Rooms

I have a new hot water system in my house. One hot water zone has 3 bedrooms of almost the same size on it. When outside temp gets to 45 degrees or so and the system turns on, one of the bedrooms seems to get about 3-4 degrees hotter than the others.

The hot bedroom has 2 windows and a Sunrad radiator that is about 40 sq. ft. Its radiator is hotter to the touch than the neighboring bedroom. I assume that this is the first radiator in the loop.

The neighboring bedroom has 3 windows and is a 10 % bigger and has the same size Sunrad radiator as that in the first bedroom. There is probably 15 ft of 3/4 copper pipe connecting the two radiators.

The third bedroom has a free standing radiator. I am not sure of the area. It has two windows and is the same size as the first bedroom. The thermostat is in this room. Pipe from the second bedroom goes down to the basement, across, and then up to this room, so there is probably 50 ft of pipe separating it from the 2nd bedroom. It is roughly the same temperature as the 2nd bedroom however, at least in the weather that we have now.

I am guessing that the total length of the entire loop is 170 ft, including the radiators. The pipe is 3/4" copper.

Is there any way to get the temperature in the first bedroom to be closer to that of the others?

When the outside temperature gets colder, will the room temperatures become more unequal? Or, will they tend to equalize as the system runs more?

System is a 175,000 btu furnace with 1 Taco 007 circulator and 7 zone valves serving different zones. Each zone is a single loop with radiators in series.

The Sunrad radiators have an open area underneath them.
Both pipes to each Sunrad radiator come out of the floor in the middle and then go out to each side. Would it be feasible to put a valve connecting the pipes where they are close so that I could bypass the radiator somewhat? Would this be noisy? Right now the system is quite quiet.

Is there any way to speed up the water flow so that the temperatures in the radiators are more equal? I do not want to mess up the other zones.

Any other ideas?