I have a 6 year old red-footed tortoise that seems very healthy, good appetite, and nice smooth growth. But about once or twice a day she will develop clear bubbles over one eye, which does obscure her vision. If I spray her head with water, it washes away the bubbles and her eye looks completely clear. No apparent eye damage, no nasal discharges. Has anyone experienced this in a tortoise, and any thoughts on cause or significance?