I was doing a search regarding low platelets and metacam, since that drug seems to be causing my GSD's nose to bleed and gums to go pale, when I came across your thread.
PLEASE treat your dog for an ehrlichia/anaplasmosa-like organism. Doxycycline at 10 mg/kg (roughly 5 mg/lb), twice a day is the aggressive dose, perhaps even IV doxy initially, though I don't have experience with doxy in that form.
Tick tests often have false negatives, assuming that we have a test for the right organism. The immune supressant drugs are driving the infection deeper. You won't have the benefit of titers to determine response, you'll have to look at cbc numbers to monitor. Sometimes you will also see changes in the blood count differential. It's important to use antibiotics that are effective against the ehrlichias for this. If that is not effective, then look to drugs that are effective for Babesia.
Good luck, hoping for the best for your Husky!