Also, check your cables, input and output sockets on pedals, power supply to pedals - check everything from the bass onwards in your signal chain.
P.S. the EQ section on that amp is a Fender style tone stack, I seem to recall that the mids are 'cut only' - meaning when the mid knob is up at full, then you're not boosting any frequencies, merely not removing any.
I think 'flat' was Bass at 10 o'clock, Mids on full, and treble at 10 o'clock.