Did you dig this tree up or was it in a pot Speedy? I dk what your weather is like but watering every day and feeding root promotor every week sounds a bit excessive to me. The water needs to be getting down to the roots. A length of plastic pipe inserted down to where you would expect to find the roots (ideally plant the pipe with the tree) and water once a week. I have found from experience that a lot but less often is better than a little water given frequently in insufficient amounts. Larch is deciduous maybe it has gone in to hibernation early. There is a disease affecting larch "Phytophthera" it is described on this link. http://www.forestry.gov.uk/pramorum
I use sterilised bone meal when planting to promote root growth - just mix it in to the back fill soil. Some states have advisors who might be able to help you. Do let us know how you get on.