Welcome to the forum, Max. I agree with Lloyd's advice. You also might try cleaning the bulbs with a wire brush. Check the sockets too. If they take the old automotive bayonet style bulbs, you can try cleaning the sockets with one of the wire brushes shaped like a cone or Christmas tree that is made to clean battery terminals.
2013 Silverado 2500HD LTZ CC 6.6L Duramax Diesel
2014 Sunset Trail SF270BH
Holly & Buster, mini Dachshunds
2016: 1 trip, 3 nights in 1 state, 316 miles
2015: 5 trips, 18 nights in 3 states, 2707 miles
2014: 5 trips, 14 nights in 3 states, 2426 miles