I'll put my money on the tap.
Second brew I did infection.
Used a dowl to knock the inside of the tap apart & presto full of shite.
Hope you get it sorted do a search on cleaning & sanitation good luck.
the rudest one
Another thing to look out for in relation to the tap:
After getting your samples, have you cleaned out the tap? The brew could be all good but then it can get infected from bacteria that has grown in the residue left. A touch of vodka on a bit of paper towel and a quick wipe before and after sampling stops this from being a problem.