What would make just my kitchen sink lose pressure after I replaced the seats and springs in my bathtub

Check aerator, may have dirt in it.

Chuck

what would make just my kitchen sink lose pressure after i replaced the seats and springs in my bathtub

In working on the tub faucet you have dislodged some minerals built up in the pipe walls that got pulled back into your system. Follow Chucks advice and check the aerator first. If there is still a problem shut the water off, open up the valve and remove the cartridge, Check and clean the inlet ports and then turn the water back on to flush out the supplies. Reassemble and test. Pressure better now? Good luck, Tom