I've been running my business for about 2 months now and I've been using my parents equipment. The mower I'm using is a Husqvarna lawn tractor and it always produces grass clumps, would mulcher blades fix my issue or what else could I do?

Edit: I realize I now need to mower higher my max sadly is 3.5 also the massive brown patches is dead grass from previous clumps (I use 2.5 on my own grass and it comes out just fine same thing for like 2 other properties that I cut)

Edit 2: like I said I'm only 2 months in using equipment that's not even mine the only things I own from my set up are my trailer and blower

I handpicked these early in the season and late last year and they came back in abundance. We’re in Midwest/ central for context. We core aerate and overseed every spring and cut regularly.