I'm having issues with my hydraulics. When I change my hydraulic/transmission fluid and filters, the hydraulics work great for about 2 hrs. Then the hydraulics diminish and become jumpy. I used the tractor supply hydraulic/transmission fluid and a Fram PH8A filter. When I check the fluid it has an light greenish color to it. What is causing this to happen? I put a tarp over the tractor thinking that water was creeping in, but it still happens. I've done this at least 3 times but it continues to happen. I've done everything that I can think of to fix it, but it continues to happen.