Probably a thrips infestation

did you buy live plants.. or just bulbs???

why are they potted and not in the ground .. does the pot have drainage..

can we see a pic of the whole plant and pot ...

ken

Bugs. Remove the plants from soil. Wash down the leaves and roots. Plant in good, clean soil in a cleaned pot, or get them in the ground in a suitable sunny spot. It's common for stores to market plants in cardboard/plastic containers where mites, white flies, and other bugs flourish. Only solutions are to throw away container "packing/soil" and rinse before planting or use bug sprays (and we surely don't need more chemicals).

The leaf damage shown is a very clear indication of thrips, one of the most damaging of gladiola pests. Typically they will appear spontaneously in the garden but it is also possible to purchase packaged corms that are already infested. Just rinsing may be insufficient to kill any lingering larvae so soaking for a couple of hours in a dilute bleach solution (4 tsp/gallon of water) before planting is suggested.

And no reason at all why not to grow glads in a container, especially in areas where they cannot be left in place over winter. Makes lifting and storing for winter so much easier!