i fly them 5 time a week and feed them about 1 ounce a day i have been feeding them a bit more corn becouse its been very cold but they have been like this for some time also they sarted to go up hight some time ago but not no more but are healthy
I would look long and hard at what you are feeding them. Increase corn and barley in their feed. Decrease peas and protein. You may also be feeding them too much. I would try this before you hit them with meds for respiratory. I was having the same issues a few years ago. I bumped the corn up to about 30% and they started flying longer. If you have a good source of barley use it first. Many of the racing mixes out there are just too protein/pea rich. Their are some feed ideas on Van Elsaker's page. I would google it.
It sounds like your birds are in good flying condition since you have been flying them regularly. If so I'd say they are just getting bored and lazy. I'd put them on the road. I want to sress: ONLY do this if you know the birds are healthy and physically fit.