I thought I will share one of my recent problematic experience with VTOL tiltrotor and the remedial steps I am taking to solve this problem (in hopes that it’ll help you). We are currently in the process of testing one of our long-range tiltrotor quadplane builds (for commercial purpose), but it’s not really a Nimbus VTOL conversion - see picture attached.
With an AUW of about 5.2 kg, the initial hover drew under 30A (which is good). However, when we inspected the flight log, it was pretty clear that the two (VTOL) low-kv rear motors were working relatively harder (and at some point, one of them was even saturated due to the yaw it was fighting at the time), but the front tilting motors were not working nearly as hard. However, I know for a fact the our front (tilting) motors are capable to supplying up to 4kg of thrust (each), but the rear motors, on the other hand, although very efficient, can only produce up to about 2.4kg of thrust (each).
So here’s what I am doing to solve this problem: I am decreasing the lever arm of the front tilting motors - that way the front motors can do a fair bit more of load carrying (for the same turning effect they cause) - I hope I made myself clear. In your case, like Greg suggested, it may the location of the CG relative to the front and rear motors combined with your front motor/prop combo. If this is the problem, you could perhaps either go up on the front motor size to something like 3520 and/or even better if you could make the distance from the front motor to the CG a big longer.