Hello! Three months ago, l bought for my 5-string Cort Curbow a new set of strings (d'addarioXL). Then l joined a doom/stoner band. The 2 guitars and me, tune our instruments at C standard. The way l tune my 5-string bass is: from B.E.A.D.G. --> C.F.A#.D#.G. So, l tune half a tone up instead of going 4 down. The type of my strings is "fat" (l remember they had on store available and a thiner version). After these tree months, l think my bass neck needs to be re adjusted, because when l play on the first fret of every string the sound is weird. And also when i switch back to standard tuning, it feels like all strings are on the neck and they feel very loose when playing. Soooo.. any advice? Is truss rod the problem?