Lower pressure on new bathroom

I'm a senior citizen if that matters. Have a well 660' deep 4gpm. Pressure and volumn in house good. 1/2" copper pipe. Added another bath on second floor (have one on 2nd floor before remodel) and plumber used 3/4" PEX (?). Pressure and volumn in new lavatory and tub is much less. Distant to new fixtures are within 10' of old. He branched off old line under house to run new. Can you explain why?
Best regards, Larry Macomson. 10-03-09.

New shower heads and aerators on faucets are more restrictive.

When you change the shower head and faucet in the old bathroom you can expect less flow too.

Changing the shower head should make a difference, if you can find a high flow head.