you might want to also try the houseplant forum ...

are you letting it near dry.. in between waterings???? use you finger to find out ... how did you come up with a deep heavy watering once a week???

shedding a few leaves.. could be transport shock ... from a nice cozy greenhouse to your house [moving it from grower.. to wholesaler.. to your house] .. with changes in both light levels..and humidity ...

any air conditioning hitting it??? .. cold air movement???

ken

I'm still new to maintaining my houseplants...so don't take my advice for definitive truth. Yours looks similar to what mine does and here is what I've concluded is the likely issue:

Improper soil drainage. Many users have noted that even their local nurseries tend to use soil mixtures that are 1 part peat, 1 part perlite or some variety of that. The soil really ought to be (per Al's suggestion) 5 parts pine bark fines, 1 part spagnum peat moss, 1-2 parts perlite with garden lime. The pine bark fines help aerate the soil and allow the roots to breathe. A good article on that can be read here.

Maybe it's an issue with the roots as well? Or a mixture of the roots being overcrowded & drowned in water?

When the leaves get curled on a monstera, it could be a sign of low humidity. Maybe try misting the leaves more or using a humidifier?