Fatsia Japonica issues help required

Donna Littler

I have 2 japonicas bought last year which were put in pots. I had them in the summerhouse over the coldest of weather and they were doing ok, even started to sprout new leave growth. I put them back outside a little early I think and the new growth went black, turned crispy and died. It looked like as the weather has improved that the plants were attempting more growth but is has also withered away and died back. I went out this evening to trim off the dead new growth and have cut it off the best as I can at the same time my hands got covered in a red sap . It also seems now that most of the established leaves are dying as they are turning brown. Any tips on how I can rescue the 2 plants ?