Good for you! I don't do tri, so don't know much about the specifics that might arise. Try over in the tri forum. It could be that running has something to do with it.

It's still winter, so I assume you're doing weights and spin class. I used to do spin class, but don't anymore. There've been a couple of big threads about spin classes on the 41 and the Over 50. My position is that they're not necessarily a good thing because the flywheel effect creates an unnatural pedal stroke. I much prefer resistance rollers or a trainer to spin bikes. There are spin bikes with a freewheel which don't have that flywheel effect issue, but I've never seen one in a spin class. It's vaguely possible that changing from a flywheel fixie spin bike to a road bike creates a different pattern of muscle contractions for which the muscles are, in a way, untrained.

At this time of year I spend one roller session a week doing a lot of one-legged pedaling. I think that's helpful. I spend most of my roller sessions just doing steady-state zone 2. Most weeks, the only intensity Stoker and I do will be a 30-70 mile ride on our tandem outside on one weekend day, where we'll go absolutely all out 'til we can hardly walk at the finish. Since it's winter, we'll take no electrolytes and drink maybe 1/2 bottle of a malto/protein combo each. Stoker will sometimes get a cramp if it's been a big jump up, but I never do, probably because I get in more roller hours during the week.