There is no doubt that more pressure results in less traction, but there are so many factors involved here (not to mention that as you mentioned, you also changed the suspension settings) that it's hard to tell. It's possible that the road also had something to do with it, especially since this is in an urban setting.
You can experiment with different pressures, usually going up/down 2 psi will make a significant enough difference to tell while you are riding, but I'd recommend you go back to the stock pressure first, get a feel for the new suspension settings and after you decide whether those are good or not (and make changes if necessary), then start experimenting with pressures. Increasing or decreasing tire pressure also impacts the suspension behavior, as the tire itself absorbs significant amounts of any input before it makes it's way to the springs.
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