What kind of filter Sys do you have? What size tank? It could be an oxygenation problem. My guys were breathing rapid too & I put in a bubble wand & that did it. It could be signs of infection also. My barbs look at the gravel all the time, I think it's just what barbs do. I got many different reasons why barbs do that.
the breathing sounds like a water issue. check your parameters.
as far as the headstands go, i've learned that just what tigers do. i've decided they are the lassie's of the fish world: "whats that girl? timmy fell down a well? show me where he is!!"
Tiger barbs are very sensitive to water params. They will point down at even the smallest trace of nitrite. If they are pointing down for more then a few minutes at a time something is wrong. The ones I've kept all died after pointing down for prolonged periods of time. I'd try a 20% water change right away since they are pale and breathing heavy.
My tiger barbs do this all the time and my water is perfect!!! I think thats just what they do sometimes. I have had mine for MONTHS and they are ok. A water change does help most probs tho.
Deb