Very odd... I hope you dont mind me saying, but looks to me like you may be spraying a bit too heavily. The metal color only needs thin layers misted on, and the layers can be done incrementally. It is quite thin, so you must be careful.
Additionally, make sure the bottle is extremely well mixed/shook up. The pigments settles quickly, and are rather fine. If you are spraying a desaturated base mix, it may be triggering your brain to apply more than needed. Proper mixture will ensure proper application.
Another consideration is what pressure are you spraying, and with what kind of airbrush?
Other possible culprits, do you have a moisture trap on your airbrush? Perhaps trapped humidity in your air hose is diluting the metal color? If this were the case, I'm not sure how your base costs turned out, but alas, I'm just throwing out some ideas...
The only time I've had issues with Vallejo colors is when my airbrushed needed cleaned such that I couldn't mist the layers on with my two-stage Iwata.
And not to be overlooked... welcome to the site! I sincerely hope we can help you. I think the Vellajo metal colors are flexible and look good, even if not the best at nailing down the metal look.. be sure to keep us updated. 🙂
