How do I get the suction back on my Dyson?

Recently I've been having my kitchen renovated and while I was out the builders decided to use my Dyson (DC22 Allergy) to clean up the mess - (dust, chunks of wall plaster, little stones etc.) And made my Dyson all dusty and full of muck so I cleaned it out: Took dirt chamber apart, wiped it out, wiped all outside, unclogged floor head etc (flat out head) and it has next to no suction now! What should I do? Its only a month old.