Welcome to AC!
Well, I have to say it doesn't look very bad in your pics to me. I know it's distressing to see but some diatom algae is normal for newer tanks. It can go away all by itself. No need to panic.
How long are your lights on each day? More than 6 or 8 hours is asking for trouble. I use a timer set so the lights are on when I'm able to see my tanks. You can also split the time, say 2 hours at breakfast & 4-5 hours later when you're home again.
1 other thing to think about is a dark background. It looks like maybe you get some bright lighting from behind the tank. It doesn't have to be direct window light to add too much light & cause issues. Try to think about where & how much light is going into the tank beside your tank lights.
