Low pressure through water filter

more than likely the saddle valve...the valve you or the plumber installed to tie into the water line and shut it off for filter install. it's getting clogged up. Turn it all the way off and on again 3 or 4 times this should clean out the little hole feeding thru the valve from the pipe.
hope this helps.
take a look here...pics of a saddle valve.

https://www.doityourself.com/forum/electric-large-kitchen-home-appliances/395295-ge-refrigerator-freezer-no-water-flow-ice-maker.html

IF THE RO OR ANY T33 FILTER HAS BEEN INSTALLED HORIZONTALLY, TRY TO INSTALL IT VERTICALLY WHERE THE OUTPUT IS ON TOP. GOD BLESS.

Remove spay head from the end of the sprayer hose and turn the water on. If you have good pressure without the head, call Delta and ask for a new spray head. If you still have low water pressure without the spray head attached, call Delta and ask for a new ceramic disc cartridge free.

It sounds like there is quite a bit of sediment in the water. The filter you are using may be a very fine micron 5-10. Try using a 30-50 micron filter.
RJ

Watch the video http://www.appliancepartspros.com/ge-water-inlet-valve-wr57x10032-ap3192626.html

sounds like you may have a little debri on hot side stem or kinked hose between valve and spout turn off water to house remove handle pull bonnet and remove stem turn water back on with stem removed see how water flow is be careful turning water on you could make a mess i am assuming the low pressure is in shower only

check for proper flow and pressure on water supply line

first off replac ethe water filter in the unit this will slow down the flow

common low flow is a kinked line or a bad water valve, the solioid valve has a filter that may be dirty. then go from there

Sounds like too much water pressure or, more likely, the coupler has worn down. You can get a replacement at most hrdware stores.