one of them has solid grey under the tail, but the other one has solid light/yellow colour featherThey look like 2 males to me.
Look at the underside of their tails - if they are barred, they are females or babies. If they are solid gray, like they appear to be, then they are males. Males do tend to be more vocal than females, but that alone is not a reliable way to tell gender.
They would benefit from some more perches and toys in the cage. A plastic perch like that can eventually hurt their feet if it's the only perch.
Thanx for your valuable reply.....I am going to keep them Btw I named them Sidr and Rashmi.At only seven months of age, the only way to be sure is with DNA. However, the one bird seems to have some light colored tail feathers and lighter colored orange cheek patches, as well as some squiggly white pied neck markings, trending towards the bird being a hen. The other bird definitely looks like a Normal Grey cock bird.
Again, at only seven months, breeders usually use singing behaviors to point out the cocks. Hens usually say squat before 9 months. They look like healthy, well bred cockatiels. What have you named them?