Too much pearling ?
I reduce my light if I want less growth.
I've recalled with some substrates or shallow depth, that plants would not stay down. Riccia often would pull loose after the water changes if not well trimmed etc.

I think the exposure to air in the non CO2 planted tank is part of the issue about why it might be bad every week or two etc. And in some cases, much less of an issue if the tap have low CO2/you allow the water to sit over night etc prior to changing the water.

We have sonme serious issues in evaluating tap water changes due to the many variables Tap water has.

Some has high Copper
Some has high CO2, some low CO2
Some folks use cold tap
Some have PO4 sometime of the year
Some have varying conditions in the tank

Hard to say as folks seldom test their tap water every time they do a water change




Regards,
Tom Barr