The new premium towels are soft and fluffy, but they will be stiff and harsh after use for a while. The most likely probability is because of hard water. The simple definition of water hardness is the amount of dissolved calcium and magnesium in the water. Hard water is high in dissolved minerals, largely calcium and magnesium.
When washing towels with hard water, it not only wastes soap/detergent and is not easy to clean, but also makes the fibers brittle and fragile. This is because the calcium ions and magnesium ions in hard water react with soap [the main ingredient is sodium stearate (C17H35COONa)] to produce calcium and magnesium fatty acids that are difficult to dissolve in water. Washing towels with soft water not only saves detergent, but also reduces the abrasion of the clothes, so that the clothes are soft and the color remains longer. So use soft water if possible.
As we know the reason of what make great towel turn into ugly, we can try to turn the hydrochloric insoluble in water to the other hydrochloric which can be soluble in water. There come to our minds are vinegar and soda.
Firstly wash with hot water and some vinegar, regular washing and drying, nothing else.
Second, use soda substitute for vinegar wash again, same procedure.
Then you will get almost brand new towels again.