be careful. One of the issues you can run into is you really have no idea what the MG has been giving them. Nutes are not about finite amounts, they are about what the plant can handle, and a large factor to what they can handle is what they are currently used to. You have no idea what they are used to, so really the best way to go is to start out really light, like maybe 1/4 recommended dosage, and taper up over a few weeks. However, this late in flowering you don't have a lot of time, so you might choose to go faster. Just realize that the possibility of a burn is going to increase. Also if you are late in flowering and the plants look healthy (not losing too many leaves, and staying bushy) you might find you don't need macro nutes. The last few weeks of flowering you typically cut them off to let the plant soak up nutes from itself.