Check outside water pressure to house. Should be 65 - 75 PSI. If good most likely the cartridge. Older faucet, do both sides to prevent future problems. Blade handles? Make sure you get Hot & Cold stems, they turn the opposite way with blade handles. Some cartridges are universal and can be adjusted to work either way. After removing the stem, check with a flashlight in the valve, delta has rubber seats and springs on many of their models. If so, replacement of the rubber seats may do the trick.

Many of these problems develop from poor maintenance on water heaters and high pressure. Water heaters, regulators, safety valves, supply lines, and emergency shut off valves at fixtures should be checked, cleaned and adjusted on an annual basis. Your local expert plumbing contractor should be able to assist you on that.