My mug cracked and leaked sticky redish/brown goo

Hi! I'm new to the forum and am wondering if anyone can help... A friend gave me a ceramic mug as a gift. It has very light pastel colors with glaze over it. I have been using it for hot and cold liquids for a while, but just noticed tonight, as I was drinking hot Robioos tea with it, brownish/reddish sticky goo (herein called BRSG) (kind of like a syrup sap from trees) started leaking or leaching out of hairline cracks either from the glaze or the ceramic itself. I started noticing the hairline cracks everywhere on the mug now. I became alarmed, because they were forming more at the mouth of the mug and I must have ingested some of it. I dumped out my tea, wiped the BRSG off with water. Then poured cold water and microwaved the mug for 1.5 minutes and the BRSG started forming again out of the cracks, and this time perhaps more cracks have formed. I'm beginning to think that this BRSG is coming from the ceramic itself. Does anyone know what is happening and if this BRSG is toxic or not? --Thank you!