There is issue with SteembotTracker Delegation Tool, may be because of this update:

In addition, the delegation manager also takes into account SP tied up in a power-down when calculating the max amount available to delegate, since SP being power-down cannot be delegated.

If my account has 1000SP out of which I delegated 500 to some account say @spydo and now I want to increase/update my delegation to 600SP, since the effective SP left in my account is 500 and I want to Update delegation to 600 SP, the tool is returning this error message: which I think should not be there since I want to Update my delegation and moving it from one account to another.