When reviving a calibrachoa, you should first look for signs of root rot. If your calibrachoa plants have brown or mushy roots and their leaves turn yellow and are dying, there is probably root rot. You can save your plant if the root rot is not too severe. First, you should cut off all the affected roots. This will help keep the damage to your plant to a minimum and give it a good chance of getting better. Next, remove any wilting leaves and leave healthy ones on your plant. Give your calibrachoa a fresh start by moving it immediately to a new pot with fresh soil. After you've done the other steps, provide the plant with an adequate amount of water and air to give it the best chance to grow back. If too many roots have black tips or almost all of the roots are slimy, your plant may not recover. When that happens, you should just start over with a new one.