panels seem to commonly come with a two-pin version of the type of connector used - with four pins - for simple trailer lights
. Now, which pin is which?
Some sets are wired so that each panel as an "in" cable and and "out" cable, so you can string them together. Others, like the Coleman set currently in our local Costco, have an "out" cable from each panel - these cannot be connected to each other, and are intended to connect to an "octopus" type cable to gather them all in parallel. The way those two-pin connectors work, to identically setup panels would connect + to - and - to + if you plugged them directly together... that's not good.
Can you show us the connections of each panel, in a photo, installation guide, website... ? How about the model numbers of each?
I don't know if blocking diodes are really needed; I suppose it depends on how badly they are mismatched in voltage output. A diode will always drop some voltage, so for optimum performance I would not want to add them unnecessarily. Maybe a diode on only the panel most likely to not keep up...
The 30 W Eliminator is a single-crystal type of panel; the ICP product is likely amorphous. That means they're likely not well-matched in characteristics. See Solar Power, ICP Solar website
for a previous discussion of this topic.