Back to Noob status

[Anthonyexmouth]

ok, so it's been 6 months since i too the cover off my imaging rig in the garden, got 5ish hours last night, 40 mins on the Flame and the rest on M101. Now when I came to stack it seems somethings happened in the intervening months and my darks/flats and darkflats don't match my lights i've just taken. APT is now recording the gain as 1.0 and when stacked with calibration frames its gone all purple without calibration frames the colour seems fine. This is cropped a little and stretched in Gimp just to show  the colour is ok. 

Any ideas what I might have done or forgotten to do? 

Setup as in the sig, capturing with APT and stacking with DSS.