I discovered a few things...
Too many "X " blocks all together did not look good, in fact they look v. confusing & messy!! So I added in the plain background blocks to calm it down a bit.
Then I realised that there needed to be something that kinda tied them all together visually. So I added more of the grey solid where ever I could!!!!
I also alternated pattern backgrounds with the plain, apart from in two places!!
And, just for fun, I did one block with 2 crosses!!!