Strange ranking occurrences in Google (NL)

[JarnoNijzing]

Mozzers,

I got a question for all of you. Recently (about 3 months ago) I launched a renewed website for a costumer of mine. Since then rankings have been improving and some decreasing a little but overall it went quite allright.

_Still, we now have some issues with some new pages and I really don't know what to do any more. _

The Case:
For starters lets say the company sells vacuum cleaners. We now make pages for specific product ranges e.g. Miele Diamond vacuum cleaners which in turn tells something about this product range and has links to different pages of that series, for instance the Miele Black Diamond Silent Vacuum Cleaner.

Why did we do this? We already ranked for specific product pages but also wanted to rank for more general terms and thus product ranges.

What happened? We now rank perfectly well for the product pages itself but for some reason the Miele Diamond Vacuum Cleaners page doesn't rank at all or not as it should.

Why is this strange? Because we applied the exact same tactic for some other product ranges on the same website and it worked like a charm (part of the reason why we started to do this for all product-ranges).

I could really use some help here. If you want I can message you the pagelink in PM but I won't post it here for several reasons.

The Vacuum Cleaners in this example or not the real products though but used as an exemplar. I really do hope to hear from you with some advice or request for more information.

Regards
Jarno