I think it might have something to do with your spring tension which might be less causing water to come out with lesser pressure. Open up the diffuser and try and stretch the spring a little bit and reassemble. That should help with the water flow.

Hi, I have been having this exact problem for the last couple of weeks. Open the diffuser with a philips head screwdriver and keep it aside. Now you will see a brass fitting with a regular screw head. Open this up(I used the wide head of a swiss knife). Be careful while opening this fitting as a small spring in there tends to fall out. Remove this spring. This has a small silicone ball on top. This is basically your valve which prevents water from dripping and builds up pressure before water can flow. Just clean the ball up and stretch the spring a little and reassemble the whole device. This should solve your problem.