PCB Etching (Negative Photoresist) Issue
Your UV lamps are fine. They have their peak output at a wavelength of 365nm (last photo), which is well in the sensitive range of most photo resists. For example, Kontakt Chemie Positiv 20 is most sensitive for 370-440nm. That's quite astonishing, since visible light starts at 380nm. 
But just check what your photo resist needs.

The next problem is the plate. Normal Glass blocks UV below a given  wavelength, but most acrylic blocks everything below 400nm. So you should first get a glass plate again. Fused quart glass would be superior since it doesn't block UV down to 200nm and less, but it's hard to get and expensive.
May be, you don't need a plate. Put a drop of oil on your PCB and place the mask on it. The paper will soak the oil, get more transparent and stick to the PCB quite tight. But you need to remove the oil after exposure.

And finally, you need to find out the best exposure time for your new setup.