Here is my issue. I had some broken pipe because of the cold winter. i cut them back and crimped them off until it got warmer. The pipe were the hot and cold to my master bathroom. I Repaired the pipes but replaced the middle section with half inch pex. So it copper to pex back to copper. the only change now is I added a T to the cold water for my fridge. All my connection are done with sharkbite. the shower and toilet are first in the run and they are working fine. my sink of the other hand has very little pressure. what could have happened?