Assuming it has A/C lift, the You have dirt or filings in the REL-2 valve. Sometimes it's the PODS-1 valve, or could be LS1 valve. They are all located at the rear of the main manifold. There is some writing on the manifold beside each valve telling you what it is. If the Aux got slow all of a sudden, there is most likely dirt in the system. Did you replace hoses or a filter lately? Sometimes filings from the free lift cyls get into the valves. The REL-2 valve is adjustable. Remove the rear cap and turn clockwise to increase pressure. Some oil leaks out. I've had to replace many valves if adjusting didn't work. Taking the valve apart and cleaning it can work too. 3 to 3.5 seconds is a normal time to reach in or out all the way.

By all Aux functions you mean reach, ss, and tilt? Make sure P1 pump is working, take some readings at G2 with a 5000 psi gauge, I would check relieve valves. Can you be more specific, does the functions slow down with the lift up or down, maybe a short on the mast cable I will inspect the cable just in case, but I am more inclined to a hyd problem.