That first pic does not appear to be slimy - that's dense GHA, when you scrape it off, it might get gooey and such, but I wouldn't call the slime growth.
First, max the intensity
Second, max the photoperiod
Third, don't clean every 7 days necessarily. That's not a rule.
Fourth, when you do clean, don't do it aggressively. In fact, clean like this:
Tic-Tac-Toe on one side, cross-cross on the other. You can do this every 7 days if you like. It's more of thinning out than cleaning.
Growth sometimes comes in stages, you might be in one, The dense growth tends to shade the screen and lead to algae completely letting go, the above cleaning helps mitigate that
How old is the scrubber?
How close are the LEDs?
Pics?