Wires overheating, AUX lights

HI Why are my wires overheating? I'm hooking up some auxiliary reverse lights on my 16 Tacoma I had this set same set up on my 07 Taco with no problem Once all hooked up two of my connections are causing the wires at the join to overheat. to hot to touch by hand. yes the connections are tight. Currently our hook up to see if we are getting power is by running jumper cables directly off the battery to the wires. We are running 2, 55 watt bulbs. one in each light and using wires that are the same gauge as a Trailer wire set up. the connectors are similar gauge. We have an inline 15 amp fuse. Can anyone lend some thought on why the wires are overheating?

If the connection is definitely good, the only thing it can be is the wire is too small. The lamps are drawing between 5 and 6 amps each.

thanks so looking around the internet it looks like at 12 amps, 10' length I need a 18 guage wire?

and, is it ok to use a bigger gauge wire than needed? i.e. if 18 guage is what is needed can I use a 14 gauge wire as I live a long way from a shop that sells wire and I have 14 gauge here at home.

Yes, larger gauge is just fine.My ex once told me I have a perfect face for radio.