1. It's not too little grease but that the grease in the lens has migrated to the aperture housing.
2. It's gonna need the housing and blades cleaned. There is NO lube on blades or housing.
OK then.....It's possible the linkage you can access may have grease where it rotates.
If you want, a couple of drops of old fashioned lighter fluid or naptha may free it up. If not it's got to be taken(really taken) apart.