This answer post was from @jimfixer. I take no credit for this answer and all the credit goes to him.
Once it dried out the corrosion on the inside began and is now causing problems . If you had taken the phone apart immediately after the water was introduced you could have cleaned the logic board and then you could have saved the phone but it is probably corroded beyond help now . This is my pet answer for wet phones you can try this it may help . If you have access to a sonic bath put the logic board it there to clean it ,if not then try the following
Clean every connection with a soft toothbrush. As well clean the logic board; use a 99% isopropyl alcohol for all cleaning. Now is the time to start drying out the phone. Set the screen in a desiccant or silica gel leave it in for several days moving it from time to time to get the max effect from the desiccant. Use a blow dryer on a low heat setting to dry the rest of the phone. Only use a hair dryer once you have cleaned the phone completely with the alcohol. Do not attempt to dry the phone if it’s still wet with water with the blow dryer as this only spreads the water. Replace the battery with a new one considers the old ones done. Clean again with isopropyl alcohol let dry and when you think everything is clean and dry reassemble the phone (make sure to clean the contacts on the screen after removing from the desiccant). Once you've reassembled the phone it’s time to power it on. Hold your breath and hope for the best