Help with Models

So, I'm trying to make some scythes and spears, but I found a problem with blockbench, which is where the texture is the same for handheld and in the inventory, if you look at the trident, you can see the model of the in hand item and the inventory texture are very different. Is there a way to change this? Another problem is that even if I use the blockbench model, it darkens the texture and makes it blurry. Anyone know any way to fix this issue?