Not all regionali depart from tracks 1-6, but those directed to Pisa, for technical reasons, do.
The Regionale you plan to take in Florence is, I believe, the 18367, departing Florence at 11:53 from track 1A. Your FrecciaRossa 9411 from Venezia SL is scheduled to arrive at track 11. Assuming an on time arrival, 14 min are sufficient to transfer. If you miss it there is another regionale to La Spezia departing at 12:53 from track 3.
If you miss the connection you can take any regionale in the next 4 hours.
Your connection in Pisa, 35 min after your arrival, is with Intercity 674, directed to Milano C.,via Genoa, which stops in Monterosso. The regionale 18367 from Florence is actually directed to La Spezia, therefore you could stay on that train all the way to La Spezia, then take a regionale from La Spezia to Monterosso. It might take only slightly longer, but it would cost less.