Worsened first layer

I have an issue with my first layer, which suddenly got worse.

What was always a perfect surface on my PEI build plate now comes out like the lower cube.
No changes in the parameters. Printer profile is the same, printing plate PEI is correctly set,
filament profile is also the same (PolyTerry PLA profile 220°/55°).

For me it looks like a slight underextrusion. As the rest is however pretty perfect I wanted to increase the flow rate just for the first layer. However, it seams thats not possible in BS?

Any comments on how I can get back the nice surface? Increase first layer print temperature?
Plate temperatur?

Ok, just for the records, I will answer it myself: the degradation was due to my filament capturing moisture from the air. This is pretty interesting as

  1. it was PLA
  2. we currently have winter so the air is rather dry at the moment (< 50%)
  3. it happened pretty quickly (in 2 or 3 weeks)
    After drying it in the oven I had the same results as before.

As a consequence I now store all my filaments in dry boxes, not only the sensible ones (PETG, TPU …)