I had a GSP Colony that I bought that looked sickly and was closed up for weeks. It recovered, but it took well over a couple of months.
Here are some pics.
Picture 1: When it first started opening up, about 2 weeks after I bought the colony. there is a smaller, healthier looking frag above it for reference.
Picture 2: The colony currently. About a year later. It spread so fast that it got onto the rock and started to overwhelm the smaller frag. Most of that green is the bigger colony that spread to the main rockwork. My phone's camera really struggles to render the blue light but it picks up that green real good.