Can anyone tell me it Marstrom made any design/construction changes in the hulls/blades/rudders between a 1990 tornado and a 2001 tornado?

I guess the answer is "no".

No significant changes. Boards/rudders on earlier years had vent holes to handle pressure changes. Otherwise still made of wood, same "reflex" rudder cross section & profile. Same board profile.

Hulls are all from the same mould. All are Nomex Honeycomb core. No known changes to internal structure or layups. Post 2001 boats have spin-pole bridle fittings already in the bow tips.

Actually, I seem to remember something about changes to the hull shape but it is all dim and hazy.

The Marstrom hull cross section is different than other builds. Most noticably around the aft section of the hull...Marstrom is quite rounded where others (like SailCraft) are flatter or angular. There are small variations permitted from the official section templates...but these don't give much performance advantage across all sailing conditions.

It was sailcraft that did most of the tweaking of hull shapes

Some sailors were able to recognize a 'Front fatty' or a 'Middle fatty' at a distance

That might be true for SailCraft in the UK, but I'm most familar with SailCraft of Canada...which my Dad co-ran until the late 1970's. Hull shapes were pretty consistent up until they went T-U in the early 90's. There was only one set of hull/deck moulds present when the company folded up...I know b/c we took in & stored all the left over equipement/stock for the final owner (which he never came back to claim to this day).