Thanks for the response. I've attached some images that I've found on my phone, because right now I am at some relatives and I can't go home to take some fresh photos, although those are just 3 days old photos. The first photo is with the cage that inhabits my first pair, both of the cages look alike, and it contains my yellow hen (Bella) and green male (TLB). Both of the pairs have in their cages the same exact things: two cuttlefish bones were they usually like to sleep, a water support, a swing, two food containers (both filled with seeds that contains vitamins and eggs and a lot of things), in between the bars you see some fruits leftover (they only eat them from the bars, they have there apple, orange, banana, mango, etc.) and they also had spray millet and honey sticks, but I need to buy them again as they love them sooo much.
Second photo is with my yellow hen, the one that was flying fast and now flies not so fast and gets tired quicker. From the photo one can see, I think, that she looks healthy and active as she was quite wary when I took the photo.
Third photo is with Snowflake (white male) from the second pair. Again the budgie in question regardless the breathing. Although he flies OK, not too fast and not too slow, I can hear sometimes that clicking sound he makes when breathing and tired.
And final photo is with my second hen, Furiosa, that is the partner of Snowflake. The aggressive one
And to answer your questions, I never gave them organic apple cider vinegar, their diet consists of seeds with vitamins, fruits, cuttlefish bones, spray millet and honey sticks with fruits on them as well (although I've created them specific times when they get spray millet and honey sticks as I've read that they can get fat from eating a lot of those, and all my budgies eat them like crazy when I give it to them).
And again I want to mention that I hear that clicking sound when they are tired and breath only if I hold them in my hands after they fly, If they are down that sound can't be heard, the sound is heard also for about 2-3 seconds, although the fact that Bella doesn't fly as fast as before concerns me a little. It may also be because now she sometimes lets me catch her while flying and she lands on my hands, that she doesn't fly as fast as before?
And one more question that I forgot before to ask. Can I give them dried fruits mix? I've seen some owners give it to their birds, but again, I need some advice from experienced owners.