The "red tears" are porfirin, a substance that looks similar to blood and they usually secrete when they have an allergy or an respiratory infection. Has there been a change in the bedding you usually use? Bedding is the primary cause of allergies in gerbils. They rarely are allergic to corncob, so you can try switching to that, or to unscented tissue. Once the allergy is gone, you can try another type of bedding you like better to see if they tolerate it. I suggest that you still call the vet to see what his opinion is, but still changing the bedding in these cases if usually the best idea.