Playing with home brew verticals

My homebrew 20+40 fan dipole decided to show a high swr just before the PACC contest, so I dragged out a glass fibre fishing pole from the shed and some glass fibre portable masts that I purchased a while back from a surplus depot, ran a 10m wire up the mast, connected the wire to a Wimo MTFT balun that was sitting doing nowt, attached 4 x 10M radials ( speaker wire from the local DIY store ), with the help from the TS480 internal atu, it would tune 160 - 6M ( except for 80M ) I have a 20M plastic coated metal fence between my garden and my neighbours so I connected one radial to that, then I could tune 80M with the TS480 - cool I think.

Wake this morning, snowing again, and I can only tune the top end of 80M, all the connections are still good, all I can assume is that the snow is causing the antenna to be detuned for the bottom of 80 ?? Anyone seen this sort of thing before ?

Perhaps I should ask the wife for one of those smart tuners to place at the base of the antenna for my birthday next month.

Andy