Viburnum tinus

I’ve planted out this screen with Viburnum Tinus about 4-5 weeks ago, there are a couple of existing established ones. I have watered well now dialling back to around 1-2 times per week and have put tree guards on as I live in a high wind area and we are experiencing early drought conditions, so a couple of questions for the wizards and witches out there:

1. When should I remove the tree shrouds?

2. In the last week I have noticed some lightening of the leaves, is ferticote all purpose suitable to give them some love before they are expected to flower in the next few weeks or so