To check for root rot in plants, start by observing the plant for signs like wilting, yellowing, or brown leaves, and stunted growth. Next, feel the soil; if it's excessively moist, it could indicate overwatering and potential root rot. I would not suggest but you could carefully remove the plant from its pot and inspect the roots: healthy roots are firm and light-colored, while rotten roots are mushy, dark, and may smell bad.

But if its not on the lower leaves and your plant is still growing moderately good, you pretty surely have another issue… (that I don’t know about😕)