Crate VC6212 Amp

Question

No I didn't move any wires. I bought a Boss ME-33 multieffect to run through the effects loop, and the effects are good but the tone just sounds off after using it the past couple weeks, and sometimes my Amp gain doesn't completely switch off when switching from the distorted channel to clean. I read on another site that the effects loop tube may be bad, since this controls the overall gain on the amp but I'm not sure.