Hi Prop,
Great way to resolve this issue would be platemates, they are a magnetic weight to attach small incremental weights to your D.Bs.
You should always be mixing up the variation of tricep extensions you are doing, yes one way would be crossing over to a BB.
Also look at variations with the D.B’s examples:
D.B Extension to a Press
D.B Extensions elbows out
D.B Extensions elbows in
Floor Extensions
Incline Extensions elbows out
Incline Extensions elbows in
Decline Extensions elbows out
Decline Extensions elbows in
Extension to the throat or over the eyes behind the head etc
Lots of different options its up to you imagination.
Cheers
Steve