Diamond IV LP gains seriously need to be fixed

At Platinum I, I was gaining +20-22 LP per win. Three weeks ago, at Diamond IV, I was gaining +18-20 LP per win with 8 wins and 2 losses.

I just played my first ranked game in three weeks and won. I'm now only gaining +14 LP, down from 18-20 LP. This is a huge drop, and I'm honestly afraid to even see how much LP I'm going to lose for a loss.

Why are LP gains so fucked up? The clusterfuck at the start of the season should have had enough time to settle, so there's clearly some other issue here.