Start by changing the spin on filter you found. However there can be other filters in the system that Tazza mentioned. But your model may not have it either.
Cut the filter open and look for steel or aluminum particles inside, if its full of metal, you have somewhat serious problems, ie pump failure, if you find the odd flake here and there inside, that can be normal wear
It can be a leak in the line that supplys oil to the pump (air is getting inside) or a restiction (plugged screen, filter, kinked line, etc) Many hyd systems have a screen between the tank and the pump to keep large forein debris out of the pump
Does the transmission warning light come on when you lift the loader arms. (most skidsteers have a charge oil pressure that must be in the correct range, usually 70 to 100 psi range. If it gets low the warning light comes on. A guage can be installed to verify this, but you need to get the correct pressure from a manual or dealer, Also charge pressure jumps around radically, this is normal, but it should stay within a defined range.
Mechanical failure like a pump, usually gets weaker as the oil warms up and thins out, where on the other hand if its a clogged screen on the suction side, or a pin hole in the suction line the hydraulics Might speed up a bit as the oil thins and flows better.
Hope this helps some, sorry I have no specific experience with that model.