Did premium first class have more effect than standard ?

[Men]

I have B747 with premium first class seat which fly on the route that doesn't have any competition. I have got about 70-80 % LF in first class seat. When the huge airline start to open their base and overwhelm some of my route with their aircraft that I think they all configure with all standard seat, then my first class seat has drop to 40-50 % LF but It doesn't effect my business seat.