Oscillating Amplifier
Those amplifiers have 30dB+ gain each. You need a longer, skinnier board, to keep the output tracks further away from the input tracks.

I presume the board is solid ground plane on the reverse? If not, that needs doing. The peppering with vias suggests that that is it ground, and also that you have top ground. Let's have a look at the copper on all the layers.

I don't know what the board thickness is. I would guess that the signal path through the board is not 50\$\Omega\$, as the tracks look quite thin. Rule of thumb for FR4 and 4350, a microstrip track should be 2 substrate thicknesses wide to be roughly 50\$\Omega\$ impedance.

I hope those Epcos filters are 50\$\Omega\$ match. Add their part number, or better still a link to the data sheet to your question. I notice they do filters that while the data sheet is headed 50\$\Omega\$, they require matching inductors.

Generally, your layout looks like the first RF design you've ever done. It looks like a low frequency design, with long tracks, wandering about coupling with their neighbours. 

The signal path through should be microstrip. The bias inductors should be right on top of the amps. The bias resistors should go directly to a good short decoupling C. Your decoupling caps C9, 10 etc are too long. These bias loops should be away from other stuff.