well both.
On the filler tube right before it meets the tank you appear to have a 90 degree silicon boost coupler hooking the fill tube to the tank. That should be rubber.
Then on the small vent line going from the tank to where ever you routed the line…if it is not connected back to the filler tube it should have a rollover ball check valve in it. This not so much of a huge deal, it’s just one of those “just in case” type things.
The silicone coupler though. That can make things real ugly if it is a typical silicone coupler.