Strange phenomina

I was experimenting with Arista EDU grade 2 RC paper the past couple week ends and making comparison tests with Ilford multigrade RC paper. Yesterday I was using the same lighting conditions, camera, lens opening exposure time and time of day outside in shade. This was the third session with this test, when the negative was developed it was way over exposed, (developer was also the same as before), I ended up diluting the developer to about half strength to get the right developing time and density. May be there where ultra active actinic rays yesterday.

See other post for report of Arista and Ilford negative and prints.