When using woods like pine that are naturally fairly resinous, router bits may quickly become coated in resin. Additionally, you're likely to get tar, dust, and other miscellaneous debris baked on to the bits, affecting the router's performance as well as the wood's finish.
This problem can be resolved by thorough bit cleaning. Start by obtaining a router bit and resin remover from your local hardware store or online. The solution should be prepared according to the manufacturer's instructions, then sprayed or brushed all over the cutting edges of the router bits carefully. Allow 10 to 15 minutes for this coating to dry before scrubbing the bit.