hydraulic power low?

I was using my 750 tractor today and I could not raise the front wheels off the ground with the FEL. There usually has been a sweet spot in the control where I could lift the front end 2 feet off the ground If i wanted.

I didnt have time to check the fluid level....in the past when my screen got clogged with shredded seals from a bad cylinder, the power dropped of, BUT at the same time i got shuddering and staggered movement....

there is no studdering or staggard movement now...just not the power it seemed to have had before.. I even raised the rpm up to 2000 , and it did nothing...

so as a first guess what do you think is happening?

also on another thread( i didnt want to hijack it) there is talk of ADJUSTING the psi...... is that possible on the 750 tractor?

thanks

bob