Lines lighter in the morning?

Amber

Does anyone else have issues with their frer lines being darker of a night time and lighter of a morning? I took my frer last night and got a clear bfp, then took a digital and another this morning. The digital was negative, and the frer from this morning was significantly lighter. Does anyone else have this happen? Should I be worried? (Last night about 7:00 pm on left, this morning 8:00 am on right..)