You have never heard the term "water burn" as it is a term I came up with. I have found that Tarantulas that are kept in highly humid environments such as soaked substrate with no ventilation. Can cause like a pruning effect like when you are in the water to long, which cause's the cuticle to become soft and blister. Think of it like this if you take a tire inner tube pump it up with way more air than is need it will make a bubble or blister then pop at the weakest spot being the thinnest and softest. Tarantulas run off of pressure as well and pressure seeks the weak spots. If the Tarantula is a heavy bodied T such as a blondi they may drag their abdomens which may speed this up.Just curious. What causes these "water burns"? I ask this because in my long term caring of blondis, I have never heard of a water burn.
Are the spots just patches of missing hair or are they bumps?
Question answered.I forgot to answer the question. Sometimes spiders come out of a molt with hair already missing. If there is no swelling, I am almost 100% sure that this is the case. Nothing to be worried about.
Secondly, try to find a Tarantula vet lol.