Probably not. Basis in nondeductible traditional IRA contributions comes either from you making nondeductible traditional IRA contributions to a traditional IRA (a SEP IRA is a type of traditional IRA), reported on line 1 of Form 8606 or from the rollover of after-tax funds from an employer plan (other than an IRA) which would be reported on line 2 of Form 8606 with explanation the next time you are required to file Form 8606 after the rollover.
A Roth conversion is a taxable rollover from a traditional IRA to a Roth IRA and the recharacterization of that Roth conversion simply undid the conversion (or a part thereof) as if it never happened. If there was no basis in nondeductible traditional IRA contributions before the Roth conversion, there was no basis after the recharacterization.
SEP contributions are always pre-tax employer contributions, so they don't add any basis in nondeductible traditional IRA contributions.
