Just over a week ago, I bought 4 bronze corydoras from a pet shop. I would've got more, but that's all they had. Along with these, I bought 4 more WCMM to add to the existing school, but I didn't get to quarantine them as I do not have another tank set up and they came from the same tank anyways. All water parameters are perfectly fine and stable, no ammonia or nitrite spikes, but lately the corydoras seem to be doing random little flips sideways or a spin. The movements are jerky and sudden, does not look natural. I don't know if this means anything, but they also don't often school and tend to do their own thing, and sometimes they just sit in the same place for a few minutes. All of the WCMM are acting normal and look very healthy, exploring, shoaling and flaring and eating their food. I feed the WCMM pellets and drop a small part of an algae wafer for the corydoras, they seem to love it, and they eat the excess pellets and dead plant matter. About once or twice a week they get fed frozen food, which is a mix of bloodworms, daphnia, mysis shrimp and I'm not sure what else. Water changes are done weekly of about 30-40%. Let me know if you need any more information and if you know what could be wrong with the corydoras, and if they need immediate treatment.