According to the instructions for the CT Individual Income Tax, the deduction is limited to $10,000 for a Married Filing Joint return, regardless of the number of accounts you contribute to during the year. It does also state that if you contributed more than the deductible limit that the excess contribution may be carried over for up to five years.
Here is a link to the instructions for reference, and a picture of that section in the instructions:
Form CT-1040
Connecticut Resident Income Tax Return Instructions
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