Painting Tamiya kits

No real idea, but from  your report this is  usually the result of lacquer over enamel or incomplete cleaning of mold release oils.

But as you  said you washed and primed, so could the color coats have been mix of lacquer and enamels or acrylics and enamel ?  or any of the clear coating? 

Good Luck on a solution

Here's my thought - with so many great hobby paints out there, why duplicolor? I'm stumped on what happened to your paint. The only thing I can think of is 1 - not letting the paint dry and cure longer before handling or 2 - spray painting in cold environment.

Sounds like crazing.  Try painting something else the same way as your model.  Same time between coats.  It's not the model or the primer would have acted up first.

Here's a link to a site that lists common paint issues and their causes.  It's geared more towards automotive paints but the principals are the same...

www.painterssupply.net/paint_troubleshooting_guide.html

I've had that happen in cold weather, especially if I left them out to dry in the cold, or the paint got through the primer to the plastic and crazed it.

Believe it or not, I've had it happen on a warm spring day with a semi light breeze blowing. Yeah, I got a nice coat but the cool wind messed up the coat of paint as it was drying.