For successive annealing stages the photoluminescence (PL) peaks of InXGa1-XN/GaN quantum wells (QWs) shift initially towards red which is followed by a blue. This phenomenon contradicts the usual monotonic blueshift. We have found that the phenomena can be explained properly only if we consider recombinations from the higher sub-bands to be present in the PL of the InXGa1-XN/GaN QWs, which is not usual. When a strong piezoelectric field exists across a QW, as encountered in InXGa1-XN/GaN QWs, the probability of optical transitions from higher sub-bands of the QW become more probable. In this paper this theory has been established from experimental results.