I hear you, but it's just going to be very hard to get a diagnosis without one. Hiding and avoiding light, and swimming directly into the flow of a powerhead, is indicative of either velvet or ich, and neither of those parasitic diseases is good news. That being said, rapid breathing in itself may or may not be a problem. I have an obese starry blenny which has always -- even from the point of purchase a year ago -- exhibited extremely rapid breathing. It's probably fine, even though it's beginning to resemble a swimming beach ball.
I'd set up a hospital tank at this point if you don't already have one. This can be a plastic garbage can with HOB filter and powerhead or airstone (or both). You may not even need a heater at this time of the year where you are. This will allow you to observe the fish closely for parasites, and then treat as appropriate. Methylene blue may help with respiration, but you may want to get a proper diagnosis first.
The good news is that American reefers have a wide assortment of meds available for treating diseases and parasitic infections.