CD4543B Direct LED Driving Capability
If you look at page 3, there is no resistor to be seen.

So I guess you are lucky no LED has burnt out yet.

However, you can try with a digital (or analog) multimeter, to measure the current (Amperes). A typical 3 mm LED should not get more than 20 mA (and 40 mA is absolute maximum). General rule is always to stay under 20 mA (while using continuous current).