Tetenal "3-bath" E6 is in reality 4-bath, including stabilizer at the end of the process.
Tetenal manufactures and sells some low-quality or unusable products, for example, their 2.5 liter "monoconcentrate" RA-4 kit. They even admitted the problem (after first denying it), and said they are working on it. This was somewhere in 2008.
Hence, I'm not surprised that the OP has problems with their E6 kit.
I occasionally had some small spots (blix iron deposits??) on bright areas such as skies when reusing Tetenal "3-bath" E6. Otherwise, the results were just fine, but I wouldn't trust it anymore. There are just too many "if"s.