LOD decreases when using terrain tree tool

Guys, Having a strange problem which is driving me crazy..Im new to unity so please help me out. I have a bunch of tree models..If I place them in the terrain using the tree tool of terrain editor and place some grass around it , the trees become pixelated and lose their detail..If I focus on them directly they appear normal but moment I turn my camera a bit to the side,they go blur..This only happens if I add details around the tree like grass ,fern otherwise it is fine..If I place the model manually without using tree tool, this doesnt happen..Also,the tree tool doesnt generate the coliders for the tree even though generate tree collider is checked.. Ive been using the same assets for sometime and it was fine but now suddenly this problem crops up..Ive reimported the assets too..help me I cant proceed like this